Creating HTML Templates

Problem

You want to store a parameterized template in an external file, read it in from your CGI script, and substitute your own variables for escapes embedded in the text. This way you can separate your program from the static parts of the document.

Solution

To expand only variable references, use this template function:

sub template {
    my ($filename, $fillings) = @_;
    my $text;
    local $/;                   # slurp mode (undef)
    local *F;                   # create local filehandle
    open(F, "< $filename\0")    || return;
    $text = <F>;                # read whole file
    close(F);                   # ignore retval
    # replace quoted words with value in %$fillings hash
    $text =~ s{ %% ( .*? ) %% }
              { exists( $fillings->{$1} )
                      ? $fillings->{$1}
                      : ""
              }gsex;
    return $text;
}

On a data file like this:

<!-- simple.template for internal template() function -->
<HTML><HEAD><TITLE>Report for %%username%%</TITLE></HEAD>
<BODY><H1>Report for %%username%%</H1>
%%username%% logged in %%count%% times, for a total of %%total%% minutes.

Or use the CPAN module Text::Template to expand full expressions if you can guarantee the data file is secure from tampering. A data file for Text::Template looks like this:

<!-- fancy.template for Text::Template -->
<HTML><HEAD><TITLE>Report for {$user}</TITLE></HEAD>
<BODY><H1>Report for {$user}</H1>
{ lcfirst($user) } logged in {$count} times, for a total of 
{ int($total / 60) } minutes.

Discussion

Parameterized output for your CGI scripts is a good idea for many reasons. Separating your program from its data lets you give other ...

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