Have a look at tachyon's Simple Module Tutorial for info on modules.

My take on this would be to put the CGI.pm query object in the 'common code' module too. That way you only have to 'use CGI;' once.

One way:

#!c:/Perl/bin/Perl.exe

use strict;
use warnings;

use MyCommon qw($q check_login common_footer);

my $log_in = check_login();

print $q->start_html(-title => 'log in');
print $q->p($log_in);
common_footer();
print $q->end_html;
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MyCommon.pm would look like:

package MyCommon;

use strict;
use Exporter;
use CGI;

our (@ISA, @EXPORT_OK, $q);

@ISA = qw(Exporter);
@EXPORT_OK = qw($q check_login common_footer);

$q = CGI->new;

sub check_login {
  return "login ok";
}

sub common_footer {
  print $q->p('common footer');
}

1;
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