This is the skeleton of something you might want to do with your template. Please take Anonymous Monk's advice and use HTML::Template's built-in functions instead of concatenation.

#!/usr/bin/perl -T
use strict;
use warnings;
use Carp;
use HTML::Template;

open my $file, "<", 'file.txt';

while (<$file>) {
        chomp;
        my($fn,$ln) = split /\t+/, $_ or carp "Row unreadable.\n";
        push @loop_data, { firstname => $fn, lastname => $ln };
}

my $template = HTML::Template->new(filename => 'template.tmpl');

print "Content-type: text/html\n\n";

$template->param(printlist => \@loop_data);

print $template->output;


<!-- Relevant part of a template: -->

<table>

<TMPL_LOOP NAME="printlist">
   <tr>
      <td><TMPL_VAR ESCAPE=HTML NAME="firstname"></td>
      <td><TMPL_VAR ESCAPE=HTML NAME="lastname"></td>
   </tr>
</TMPL_LOOP>

</table>
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