Dump the column that you want to create the drop-down menu on into an array, then pass a reference to that array to a CGI object, thusly:

#!/usr/bin/perl -wT
use strict;
use CGI;
my $q = new CGI;

#Other stuff that works with with an excel file and creates the array 
+. . .
#which is probably the stuff you were looking for here. . .


print 
  $q->header(),
  $q->start_form(-method =>'get', -action =>'/cgi-bin/script.pl'),
  $q->popup_menu(-name=>"column",-values=>\@array_you_made), 
  $q->submit("Go!"),
  $q->end_form();
[download]

Actually, looking at this, the hard part might be making the array. I'm not sure, I've never worked with Excel via perl.