$CGI->popup_menu returns a string that you have to print yourself. This seems to work when I run it:

#!/usr/bin/perl -w

use CGI;

my $CGI = CGI->new();

%OS_APP_NAME = (
                        'AA'  => 'HP-UX',
                        'AB'  => 'SunOS',
                        'AD'  => 'Linux',
                        'AJ'  => 'Windows 2000',
                        'AK'  => 'Apache',
                        'AM'  => 'IIS',
                        'AP'  => 'VMware',
                        'AR'  => 'Windows 2003',
                        'E'   => 'AIX',
                        'MC'  => 'ControlM',
                        'QD'  => 'DYNIX',
                        'X'   => 'Tandem'
                );

print $CGI->popup_menu(-name=>'TECH_SPEC_ID',
                       -values=>\%OS_APP_NAME);
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If the missing print is not the problem, I don't know what is.