#!/usr/bin/perl

use CGI qw(:standard);
my $q = CGI->new();

## all your form data is now in $q

use HTML::Template;
my $template =
  HTML::Template->new( filename => '/path/to/file.tmpl' );

$q->param(
    -name  => 'foo',
    -value => uc( $q->param( 'foo' ) )
);

## change a parameter in-place

$template->param(
    templatefoo => $q->param( 'foo' ),
    templatebar => $q->param( 'bar' )
);

# insert whichever form data you need into the template

print $q->header();
print $template->output();

# and we're done