You could use any of the various html template modules or just print a here document...

#!/usr/bin/perl -w

use strict;

my $text = "Display this";

print <<END_HTML;

<form action="blah.pl">
    <input type="text" name="stuff" value="$text" />
    <input type="submit" value="Submit">
</form>

END_HTML
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Here's a basic layout that I would offer you.

#!/usr/bin/perl -w

use CGI qw/:standard :html3/;
my $q = new CGI;
my $var = "100";

print
   $q->header( -type=>'text/html'),
   $q->start_html(),
   $q->start_form(-method=>'post',
                  -action=>"another.cgi"),
   "Enter Item Number: ",
   $q->textfield(-name=>'var_data', -size=>'6',
                 -value=>"$variable"),
   $q->end_form,
   $q->end_html;

exit;
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This will put data in the textfield and will allow the user to edit it before moving onto the next script (another.cgi).  Note, the commas, semi-colons, quotes, and double-quotes are not arbitrary.  You also need to have the CGI perl module installed on your server--I don't think it's standard issue with Perl.

That's Spenser, with an "s" like the detective.