Trivial SSCCE:

#!/usr/bin/env perl 
use strict;
use warnings;
use HTML::Template;

my @sources = (
    "Hello <TMPL_VAR NAME=FOO>\n",
    "Goodbye <TMPL_VAR NAME=FOO>\n",
);
my @templates;

# Create and populate 2 templates with one loop
for my $source (@sources) {
    my $tmpl = HTML::Template->new (scalarref => \$source);
    $tmpl->param (FOO => 'StrangeDucks');
    push @templates, $tmpl;
}

# Output from the two teamplates
for my $t (@templates) { print $t->output }
[download]

See also the HTML::Template Tutorial.

(Edit: minor update to improve generality.)

I needlessly made the question too complex adding details that weren't relevant or remotely clear. Sorry about that. Let me rephrase the question. Normally, I use to create the displayed page parsing the data as necessary. What I would like to do is to create a file that can be used as the body of an email at the same time that I'm creating the displayed page. This would mean that two templates would be used at the same time. The idea to make the code easier to maintain. I hope this is a little bit more clear of my

Hi,

Sorry, it sounds as if you're not a programmer, my advice is hire a programmer