NAME
        HTML::EP - a system for embedding Perl into HTML

SYNOPSIS
        <html><head><title>CGI-Env</title></head>
        <ep-comment>
            This is an HTML document. You see. Perhaps you wonder about
            the unknown HTML tags like ep-comment above? They are part
            of the EP system. For example, this comment section will
            be removed and you won't see it in your browser.
        </ep-comment>
        <ep-perl>
            # This is an example of embedding Perl into the page.
            # We create a variable called env, containing our environment
            # variables. This variable will be used below.
            my $self = $_;
            my $env = [];
            my($var, $val);
            while (($var, $val) = each %ENV) {
                push(@$env, { var => $var, val => $val });
            }
            $self->{env} = {%ENV};
            '';
        </ep-perl>
        <body><h1>Your CGI environment</h1>
            Your CGI environment looks as follows:
            <table><tr><th>Variable</th><th>Value</th>
                <ep-list items="env" item="e">
                   <tr><td>$e->var$</td><td>$e->val$</td>
                </ep-list>
            </table>
        </body>
        </html>

WARNING
    THIS IS ALPHA SOFTWARE. It is *only* 'Alpha' because the interface (API)
    is not finalised. The Alpha status does not reflect code quality or
    stability. In particular the following things might change without
    further notice:

            The way of passing variables as attributes. For example, currently
            one can use

                <ep-mail epparse-from="$cgi->email$" to="joe"
                         subject="Test mail">

            to pass the form variable *email* into method calls. I consider
            changing this to

                <ep-mail from="$cgi->email$" to="joe" subject="Test mail"
                         parse=1>

            or whatever. The decision mainly depends on performance
            considerations and readability. See the section on "Variables"
            below.

            The C interface of introducing own methods. This depends on whether
            I need changes for inserting the module into mod_perl. See the
            section on "TODO" below.

DESCRIPTION
    Have you ever written a CGI binary? Easy thing, isn't it? Was just fun!

    Have you written two CGI binaries? Even easier, but not so much fun.

    How about the third, fourth or fifth tool? Sometimes you notice that you
    are always doing the same:

        Reading and parsing variables

        Formatting output, in particular building tables

        Sending mail out from the page

        Building a database connection, passing CGI input to the database and
        vice versa

        Talking to HTML designers about realizing their wishes

    You see, it's soon to become a pain. Of course there are lots of little
    helpers around, for example the CGI module, the mod_perl suite and lots
    of it more. Using them make live a lot easier, but not so much as you
    like. the CGI(3) manpage. the mod_perl(3) manpage.

    On the other hand, there are tools like PHP/FI or WebHTML. Incredibly
    easy to use, but not as powerfull as Perl. Why not get the best from
    both worlds? This is what EP wants to give you, similar to ePerl or
    HTML::EmbPerl. I personally believe that EP is simpler and better
    extendible than the latter two. the ePerl(1) manpage. the
    HTML::EmbPerm(3) manpage.

    In short, it's a single, but extensible program, that scans an HTML
    document for certain special HTML tags. These tags are replaced by
    appropriate output generated by the EP. What remains is passed to the
    browser. Its just like writing HTML for an enhanced browser!

  Prerequisites

    As far as I know EP depends on no system dependent features. However, it
    relies on some other Perl modules:

    CGI         The CGI module should be a part of your Perl core's
                installation. If not, you should definitely upgrade to Perl
                5.004. :-) My thanks to Lincoln D. Stein
                <lstein@genome.wi.mit.edu>.

    HTML::Parser
                This module is used for parsing the HTML templates. My
                thanks to Gisle Aas <aas@sn.no>.

    libwww      The LWP library contains a lot of utility functions, for example
                HTML and URL encoding and decoding. Again, my thanks to
                Gisle Aas <aas@sn.no>. :-)

    Perl itself and the above modules are available from any CPAN mirror,
    for example

           ftp://ftp.funet.fi/pub/languages/perl/CPAN/modules/by-module

  Installation

    Installing this module (and the prerequisites from above) is quite
    simple. You just fetch the archive, extract it with

        gzip -cd HTML-EP-0.1000.tar.gz | tar xf -

    (this is for Unix users, Windows users would prefer WinZip or something
    similar) and then enter the following:

        cd HTML-EP-0.1000
        perl Makefile.PL
        make
        make test

    If any tests fail, let me know. Otherwise go on with

        make install

    This will put the required Perl modules into a destination where Perl
    finds it by default. Additionally it will install a single CGI binary,
    called `ep.cgi'.

    The docs are available online with

        perldoc HTML::EP

    If you prefer an HTML version of the docs, try

        pod2html lib/HTML/EP.pm

    in the source directory.

  Using the CGI binary

    I suggest that you choose an extension and configure your WWW server for
    feeding files with this extension into `ep.cgi'. For example, with
    Apache, you can add the following lines to your `srm.conf':

        ScriptAlias /cgi-bin/ep.cgi /usr/bin/ep.cgi
        AddHandler x-ep-script .ep
        Action x-ep-script /cgi-bin/ep.cgi

    This tells Apache that files with extension ep.cgi are handled by the
    CGI binary `/usr/bin/ep.cgi'. Make sure, that the ScriptAlias line is
    entered *before* any other ScriptAlias instruction!

    From now on your server will never return files with extension .ep
    directly! Verify your installation by creating the following file:

        <ep-perl>
        print "content-type: text/plain\n\n";
        print "It worked! Your EP system is up and running.\n";
        </ep-perl>

    Store it as `/test.ep' on your web server and retrieve the file via your
    Web server. You should neither see the `ep-perl' not the `print'
    instructions.

  Available methods

    All EP tags are starting with the prefix *ep-*. Some available tags are:

    ep-comment
        This is a multi-line tag for embedding comments into your HTML page.
        But why use this tag, instead of the usual HTML comment, `<!--'? The
        difference is, that the user will never see the former.

        Example:

            <html>
                <!-- This is a comment. I like comments. --!>
                <ep-comment>
                    This is another comment, but you won't see it
                    in your browser. The HTML editor will show it
                    to you, however!
                </ep-comment>
            </html>

        Do not try to embed EP instructions into the comment section! They
        won't produce output, but they will be executed anyways.

    ep-perl
        This is for embedding Perl into your script. There are two versions
        of it: A multiline version is for embedding the Perl code
        immediately into your script. Example:

            <html>
                <head><title>The Date</title></head>
                <body>
                    <h1>The Date</h1>
                    <p>Hello, today its the</p>
                    <p align=center>
                    <ep-perl>
                        # This little piece of Perl code will be executed
                        # while scanning the page.
                        #
                        # Let's calculate the date!
                        #
                        my($sec,$min,$hour,$mday,$mon,$year)
                            = localtime(time);
                        # Leave a string with the date as result. Will be
                        # inserted into the HTML stream:
                        sprintf("%02d.%02d.%04d", $mday, $mon+1, $year+1900);
                    </ep-perl> 
                    </p>
                </body>
            </html>

        If you don't like to embed Perl code, you may store it into a
        different file. That's what the single-line version of ep-perl is
        for:

            <html>
                <head><title>The Date</title></head>
                <body>
                    <h1>The Date</h1>
                    <p>Hello, today its the</p>
                    <p align=center>
                    <ep-perl src="date.pl">
                    </p>
                </body>
            </html>

        You have noticed, that the little script's result was inserted into
        the HTML page, did you? It did return a date, in other words a
        string consisting of letters, digits and dots. There's no problem
        with inserting such a string into an HTML stream.

        But that's not always the case! Say you have a string like

            Use </html> for terminating the HTML page.

        This cannot be inserted as a raw string, for obvious reasons. Thus
        the ep-perl command has an attribute *output*. Use it like this:

            <ep-perl output=html>
                'Use </html> for terminating the HTML page.';
            </ep-perl>

        Possible values of the *output* attribute are `raw' (default),
        `html' (HTML encoded) and `url' (URL encoded).

        It's a common mistake, to use the Perl command `return' in embedded
        Perl. Never do that! If you need return (there are of course
        situations where returning can help), do it like this:

            <ep-perl>
                sub eval_me {
                    if ($this) {
                        return 'foo';
                    } elsif ($that) {
                        return 'bar';
                    }
                    '';
                }
                eval_me();
            </ep-perl>

        See the section on "Variables" below for interactions between Perl
        variables and EP variables.

    ep-mail
        This command will send an e-mail. The attributes will be used for
        creating the email header, in particular the `subject', `from' and
        `to' attribute should be used. Example:

            <ep-mail subject="Howdy!" from="joe@ispsoft.de"
                     to="bill@whitehouse.gov">
                Hello, Bill, old chap. How are you?

                Yours sincerely,
                Jochen
            </ep-mail>

        Note, that you can still use EP variables in the E-mail body, for
        example the following works:

            <ep-mail subject="Test" epparse-from="$cgi->email$"
                     to="joe@ispsoft.de">
                Hello, Joe,
                this e-mail was sent to you by $@cgi->name$.
            </ep-mail>

        Note that we suppress conversion into HTML format in the mail body!
        See the section on "Variables" below for details.

    ep-errhandler
        This command advices EP, what to do in case of errors. See the
        section on "Error handling" below. Example:

            <ep-comment>
                Set the template being used for system errors.
            </ep-comment>
            <ep-errhandler type=system src=/templates/syserr.html>
            <ep-comment>
                Likewise, set the template for user errors.
            </ep-comment>
            <ep-errhandler type=user src=/templates/usererr.html>

        If an error occurs, the given scripts are loaded and used as
        templates instead of the current one. You don't need external files!
        Instead you can use

            <ep-errhandler type=user>
                <HTML><HEAD><TITLE>User error</TITLE></HEAD>
                <BODY><H1>User error</H1>
                <P>Replace user and continue. :-)</P>
                <P>To be serious, the following problem happened:</P>
                <PRE>$errmsg$</PRE>
                <P>Please return to the calling page, fix the problem
                and retry.</P>
                </BODY></HTML>
            </ep-errhandler>

        However, you might prefer to use a single error template and of
        course it's faster to use external error templates than parsing
        builtin templates. (At least, if no error occurs. :-)

    ep-error
        This command forces an error message. See the section on "Error
        handling" below. You can trigger user or system errors by setting
        the *type* attribute to the values `system' (default) or `user'. The
        *msg* attribute is for setting the error message.

        Example:

            <ep-comment>
                If no email address was entered, force a user error.
            </ep-comment>
            <ep-if epparse-eval="$cgi->email$" type=user>
                <ep-error msg="Missing email address">
            </ep-if>

    ep-database
        This command connects to a database. Its attributes are `dsn',
        `user' and `password' corresponding to the same attributes of the
        DBI connect method. See the DBI(3) manpage for details on DBI.

        Example:

            <ep-database dsn="DBI:mysql:test" user="joe"
                         password="Authorized?Me?">

        You can use different database connections by using the *dbh*
        attribute:

            <ep-database dbh="dbh2" dsn="DBI:mSQL:test">

        The *dbh* attribute advices EP to store the DBI handle in the given
        variable. (Default: `dbh') See the section on "Variables" below.

    ep-query
        This command executes an SQL statement. The `query' attribute will
        be used for passing the SQL statement. Of course a multiline version
        is available, thus

            <ep-query statement="INSERT INTO foo VALUES (1, 'bar')">

        is the same as

            <ep-query>
                INSERT INTO foo VALUES (1, 'bar')
            </ep-query>

        If your query retrieves a result, use the `result' attribute to
        store it in a variable, for example like this:

            <ep-query statement="SELECT * FROM employees" result="employees">

        This will create a variable `employees', an array ref of hash refs.
        You can use the ep-list command for displaying the output. See the
        section on "Variables" below.

        When using multiple database connections, use the *dbh* attribute
        for choosing the connection. (See the *ep-database* method above.)

    ep-list
        This command is used to display an array of refs. Lets assume, that
        the variable `employees' contains a an array ref of refs with the
        attributes *name* and *department*. Then you could create a table of
        employees as follows:

            <table><tr><th>Nr.</th><th>Name</th><th>Department</th>
            <ep-list items="employees" item="e">
                   <tr><td>$i$</td><td>$e->name$</td><td>$e->department$</td>
            </ep-list>
            </table>

        This will be processed as follows: For any item in the array,
        retrieved from the variable `employees', create a variable `e' and
        display the text between ep-list and /ep-list for it by replacing
        the patterns $e->name$ and $e->department$ with the corresponding
        values.

        The variable *i* is initially set to 0 and incremented by one with
        any element.

        You must not create a variable for the *items* attribute: When using
        a *range* attribute instead of *items* then a variable list will be
        created for you. The *range* attribute can be either `start..stop'
        in which case a list of the numbers start..stop will be created.
        Otherwise the attribute must be a comma separated list of values.
        See the *ep-select* command below for an example of the *range*
        attribute.

    ep-select
        This is similar to ep-list, but it is specifically designed for
        creating SELECT boxes and similar things. We explain it by example:

            <ep-select name="year" range="1991..1995" item="y"
                       epparse-selected="$cgi->year$">
                <OPTION $selected$>$y$</ep-select>

        If you supply a *selected* attribute, then a variable *selected*
        will be created for any item. The value will be either an empty
        string or the word `SELECTED' (configurable via the attribute
        *selected-text*), depending on whether the item matches the
        *selected* value or not.

    ep-input
        This is usefull for reading an objects data out of CGI variables.
        Say you have a form with input fields describing an address, the
        field names being address_t_name, address_t_street, address_n_zip
        and address_t_city. By using the command

            <ep-input prefix="address_" dest="address">

        the EP program will create a variable "address" for you which is an
        hash ref as follows:

            $cgi = $_->{cgi};
            $_->{address} = {
                name =>   { col => 'name',
                            val => $cgi->param("address_name"),
                            type => 't',
                          },
                street => { col => 'street',
                            val => $cgi->param("address_street"),
                            type => 't',
                          },
                zip =>    { col => 'zip',
                            val => $cgi->param("address_zip"),
                            type => 'n',
                          },
                city =>   { col => 'city',
                            val => $cgi->param("address_city"),
                            type => 't'
                            }
            };

        In general column names beginning with *address* will be splitted
        into `prefix_type_suffix', the type being either 't' for text or 'n'
        for number. The idea is generating SQL queries automatically out of
        the `address' variable.

        There are situations where you want to fetch not only a single
        object, but a list of objects. Suggest an order form of articles.
        Then you might have input fields *art_0_t_name*, *art_0_n_count*,
        *art_0_n_price*, *art_1_t_name*, ...

        In that case you can give the *ep-input* command an attribute list,
        like this:

            <ep-input prefix="art_" dest="art" list=1>

        The module will read an array ref of objects to the variable `dest'.
        Any object will have an additional scalar variable `i' referring to
        the items number, beginning with 0. In other words, you can process
        the order form as follows:

            <ep-input prefix="art_" dest="art" list=1>
            <ep-perl>
              my $self = $_;
              my $sum = 0.0;
              for (my $i = 0;  defined($self->{cgi}->param("art_$i_n_count"));
                   $i++) {
                  $sum += $self->{cgi}->param("art_$i_n_count") *
                          $self->{cgi}->param("art_$i_n_price")
              }
              ''
            </ep-perl>
            <ep-mail epparse-from="$cgi->email$" to="order@mydomain"
                     subject="Order form">
              The following items have been ordered:

                Nr.    Price   Article

              <ep-list>
                $art->count->val$  $art->price->val$  $art->name->val$
              </ep-list>

              Total sum: $sum$
            </ep-mail>

  Conditional HTML

    It is possible to blank out parts of the HTML document. See the
    following example:

        <html><head><title>Conditional HTML</title></head>
        <body>
          <h1>Conditional HTML</h1>
          <ep-if epperl-eval="$_->{cgi}->param('i') < 0">
            You have entered a negative number for i!
          <ep-else epperl-eval="$_->{cgi}->param('i') == 0">
            You have entered zero for i!
          <ep-else>
            <ep-if epperl-eval="$_->{cgi}->param('j') < 0">
              You have entered a negative number for j!
            <ep-else epperl-eval="$_->{cgi}->param('h') == 0">
              You have entered zero for j!
            <ep-else>
              Ok, both numbers are positive.
            </ep-else>
          </ep-else>
        </body>
        </html>

    The example is of course somewhat unnatural, because you'd better use a
    single ep-perl in that case, but it shows that we can use arbitrary
    complex structures of conditional HTML.

  Localization

    Localization is available via the HTML::EP::Locale module. Currently it
    only offers methods for localizing strings.

    To access the module, start your HTML page with

        <ep-package name="HTML::EP::Locale" require=1>

    When the package is loaded, it tries to guess your documents language.
    The default language is *de* (german; I ought to make this
    configurable). You can specify another language (for example *en* for
    english or *fr* for french) by either supplying a CGI variable
    `language=xy' or giving your document a secondary extension like
    `page.xy.ep'. That is, if your document is called

        mypage.de.ep

    then the language *de* will be choosen, but *de* will be choosen for

        mypage.en.ep

    Two methods are available for localizing strings. For short strings like
    titles, headers or Link refs you might prefer this version:

        <ep-language de="Titel" en="Title">

    Obviously this is not appropriate for longer strings and it must not
    contain HTML patterns. Thus another version is available:

        <ep-language language=de>
          <p>Dies ist ein Absatz.</p>
          <p>Dies ist der zweite Absatz.</p>
        </ep-language>
        <ep-language language=en>
          <p>This is one paragraph.</p>
          <p>This is another paragraph.</p>
        </ep-language>

  Error handling

    Error handling with EP is quite simple: All you do in case of errors is
    throwing a Perl exception. For example, DBI handles are created with the
    RaiseError attribute set to 1, so that SQL errors trigger a Perl
    exception. You never care for errors!

    However, what happens in case of errors? In that case, EP will use the
    template that you have set with ep-errhandler and treat it like an
    ordinary EP document, by setting the variables `errmsg' and `admin'.

    If you don't set an error handler, the following template will be used,
    which is well suited for creating an own error template:

        <html><head><title>Internal error</title></head>
        <body><h1>Internal error</h1>
        <p>An internal error occurred. The server has not been able to
        fullfill your request. The error message is:</p>
        <pre>
            $errmsg$
        </pre>
        <p>Please contact the Webmaster,
        <a href="mailto:$admin$">$admin$</a>,
        tell him the URL, the time and error message.
        </p>
        <p>We apologize for any inconvenience, please try again later!</p>
        <br><br><br><p>Yours sincerely,</p><p>The Webmaster</p>
        </body>
        </html>

  Variables

    It is important to understand, how EP variables work, in particular when
    working with ep-perl.

    You always have an object $_, which is an instance of the HTML::EP class
    (a subclass of HTML::Parser). This object has certain attributes, in
    particular `$_-'{cgi}>, a CGI object and `$_-'{dbh}>, the DBI handle.
    (Of course valid after `ep-database' only.) If you want to set or modify
    a variable, you have to set `$_-'{varname}>. If you want to retrieve the
    value, use the same. Note that you cannot use `$_' for a long time, as
    it will be changed by Perl loops and the like, thus your Perl code
    typically starts with

        $_ = $self;

    But how do you access the variable from within EP documents? You just
    write

            $varname$

    This will be replaced automatically by the parser with the value of `$_-
    >{varname}'. Even more, the value will be converted into HTML source!

    If `varname' is a structured variable, for example a hash or array ref,
    you may as well use

            $varname->attrname$

    or

            $varname->0$

    to access `$_->{varname}->{attrname}' or `$_->{varname}->[0]',
    respectively. A special value of *varname* is `cgi': This will access
    the CGI variable of the same name, thus the following are equivalent:

            $cgi->email$

    and

            $_->{cgi}->param('email');

    But what, if you don't want your variable to be HTML encoded? You may as
    well use

            $@varname$      (Raw)
            $#varname$      (URL encoded)
            $~varname$      (SQL encoded)

    The latter uses the $_->{dbh}->quote() method. In particular this
    implies that you have to be connected to a database, before using this
    tag!

    You can even use these symbols in attributes of EP commands. For
    example, the following will be usefull when sending a mail:

        <ep-mail subject="Howdy!" epparse-from="$@cgi->email$"
                 to="bill@whitehouse.gov">

    By prefixing the attribute name with `epparse-' you tell the EP module
    that the attribute must be parsed before processing it. (Note, that one
    doesn't use an HTML encoded value in that case!) Another prefix is
    `epperl-': In this case the attribute will be evaluated by the Perl
    interpreter, much similar to the ep-perl method. The perl code's result
    will be used as final attribute value.

    WARNING: As already said, use of `epparse-' and `epperl-' is dangerous,
    as these things are likely to be changed in the future.

  Producing Non-HTML

    Say you want a CGI binary that creates a gif and not an HTML document.
    (See the `ifgif.ep' file from the SNMP::Monitor distribution for an
    example.) This can be done in the following way:

    1.)     Create your own MIME header, for example like this:

                <ep-perl>
                    my $self = $_;
                    $self->print("HTTP/1.0 200 OK\n",
                                 "content-type: image/gif\n"
                                 "\n");
                </ep-perl>

    2.)     Do whatever you want to create your image, for example restore it
            from a database:

                <ep-database dsn="DBI:mysql:test" user="joe" password="joe">
                <ep-query statement="SELECT image FROM images WHERE id = 0"
                          result="im">
                <ep-perl>
                    my $self = $_;
                    $self->print($self->{im}->{image});
                </ep-perl>

    3.)     Finally tell the EP module, that it must not produce any further
            output by doing a

                <ep-perl>$_->Stop()</ep-perl>

DEBUGGING
    Debugging CGI applications is always a problem. The EP module does its
    best to support you.

    Whenever you supply a CGI variable *debug*, then the module will enter
    debugging mode. For example if your document is `/mypage.ep', then tell
    your browser to fetch `/mypage.ep?debug=1'. You won't see the usual HTML
    page, but a plain text page with lots of debugging messages and the
    created HTML source.

    You may extend the debugging code with sequences like

        <ep-perl>
            my $self = $_;
            if ($self->{debug}) { $self->print("I'm here!\n"); }
        </ep-perl>

    Note that you should not call the *print* function directly, but the
    *print* method! The former works well in CGI environments, but EP should
    work even in other environments as well.

    But sometimes this is not sufficient: What's inserting debugging
    messages compared to using the Perl debugger? In that case you can
    emulate a CGI environment as follows:

        export DOCUMENT_ROOT=/usr/local/www/htdocs
        export PATH_TRANSLATED=$DOCUMENT_ROOT/mypage.ep
        export REQUEST_METHOD=GET
        export QUERY_STRING="var1=val1&var2=val2"
        perl -d /usr/bin/ep.cgi

    This allows you single-stepping through your program, displaying
    variable values and the like.

EXTENSIONS
    It is quite easy to write own methods.

  Single-line extensions

    For example, suggest you want a method for accessing environment
    variables:

        <ep-env var="e">

    The idea is to create a variable `e', which is a hash ref of the current
    environment variables, so that you can use

        $e->REMOTE_AGENT$

    for accessing the name of the users browser.

    This can be done like this:

        <ep-perl package="HTML::EP">
        my $self = $_;

        # Write a handler for ep-env:
        sub env ($$) {
            my($self, $attr) = @_;
            my $var = $attr->{var};
            $self->{$var} = {%ENV};
            '';
        }

        # Register the handler in the list of handlers:
        $self->{_ep_funcs}->{'ep-env'} = { method => 'env' };
        # Return an empty string:
        '';
        </ep-perl>

    The *method* attribute of the handler tells the EP module to call

        $_->env($attr);

    if the `ep-env' tag is used. The argument `$attr' is a hash ref of the
    tags attributes. Note the use of the *package* attribute: By default the
    `ep-perl' code is executed in a *Safe* compartment. See the Safe(3)
    manpage.

  Multi-line extensions

    But how to write methods, that use a `<tag>' .. `</tag>' syntax? As an
    example, we write a method for creating external files. The method
    receives two attributes, a *file* attribute for the files name and a
    *contents* attribute for the files contents. The method can be used in
    two ways:

        <ep-file file="test.dat" contents="Hi!">

    or like this, in multiline mode:

        <ep-file file="test.dat">
            Hi!
        </ep-file>

    Here it is:

        <ep-perl package="HTML::EP">
        # Write a handler for ep-file:
        sub file ($$) {
            my($self, $attr) = @_;
            my $contents = $attr->{contents};
            if (!defined($contents)) { # Multiline method, no "contents"
                return undef;          # attribute given; return undef
            }                          # until we are called again.
            my $file = $attr->{file};
            require Symbol;
            my $fh = Symbol::gensym();
            if (!open($fh, ">$file)  ||  !(print $fh ($contents))  ||
                !close($fh)) {
                die "Error while creating $file: $!";
            }
            '';
        }
        # Register the handler in the list of handlers
        # Note the use of the "default" attribute:
        $self->{_ep_funcs}->{'ep-env'} = { method => 'env',
                                           default => 'contents' };
        # Return an empty string:
        '';
        </ep-perl>

    In other words: The method gets called twice, once for `<ep-file>' and
    once for `</ep-fileE</gt>'. If it thinks, it should enter multi-line
    mode (if the *contents* attribute is not set, it returns `undef'. In
    that case EP is looking at the *default* attribute of the handler which
    is telling, that the lines between `<ep-file>' and `</ep-file>' ought to
    be written into the *contents* attribute. Thus this attribute exists, if
    the method is called a second time.

    Note the use of the *Symbol* package when accessing files: *Never* use
    global handles like

        open(FILE, ...)

    as this might break future multithreading code!

  Selfloaded methods

    In the above examples the extension methods have been compiled
    immediately. This is not always a good idea: For example the `ep-mail'
    method is loading big external packages like *Mail::Internet* for
    sending the mail. In such cases you might wish to use HTML::EP's builtin
    self loader, which is quite similar to that of CGI. We choose `ep-mail'
    as an example:

        <ep-perl package="HTML::EP">
        my $self = $_;
        # Create a string that can be compiled for loading the method:
        $AUTOLOADED_SUBS{_ep_mail} = <<'end_of__ep_mail';
            require Mail::Internet;
            sub _ep_mail ($$) {
                my($self, $attr) = @_;
                ...
            }
        end_of__ep_mail

        $self->{_ep_funcs}->{ep-mail} = { method => '_ep_mail',
                                          default => 'body' };
        </ep-perl>

    The advantage is that you have the method available, but the performance
    penalty of loading it is almost omitted, if the method is not used.

  Namespace pollution

    So far extensions are inserted at run time only, usually by loading them
    from external files. For example you might create extensions for
    building a WWW shop and put them in, say, `shop.lib'.

    As soon as it is possible to make extensions permanent (with mod_perl or
    an HTML::EP server) and extensions will be loaded at startup, there will
    be more and more of such extension files. Experience shows, that
    namespace pollution will finally become a problem. For example, any
    virtual Web server might have a completely different method `ep-buttons'
    for inserting an automatically generated button frame.

    Thus I propose to use a package model inherited from Perl's package
    model, and start using it now:

    If you create a shop extension, put it into a separate package,
    `HTML::EP::Shop', say. When working with the extension, use

        <ep-package name="HTML::EP::Shop" isa="HTML::EP">

    as the very first line, so that your Parser object becomes blessed into
    the Shop package. And let your shop extension file look like this:

        use vars qw(@ISA);
        @ISA = qw(HTML::EP);

        # Define first extension method
        ...

        # Define second extension method
        ...

    Note that this allows inheritage! Currently the extension file has to be
    loaded with

        <ep-perl package="HTML::EP::Shop" src="shop.lib">

    but this will change in the future. The *isa* attribute can be omitted
    and defaults to `HTML::EP'. Otherwise it is a blank separated list of
    package names, just like @ISA is.

TODO
            mod_perl support

            Create an EP server that is accessible via a small C wrapper

AUTHOR AND COPYRIGHT
    This module is

        Copyright (C) 1998    Jochen Wiedmann
                              Am Eisteich 9
                              72555 Metzingen
                              Germany

                              Phone: +49 7123 14887
                              Email: joe@ispsoft.de

    All rights reserved.

    You may distribute this module under the terms of either the GNU General
    Public License or the Artistic License, as specified in the Perl README
    file.

SEE ALSO
    the DBI(3) manpage, the CGI(3) manpage, the HTML::Parser(3) manpage

