Since under CGI you have named parameters instead positional parameters, you'll have to restruture your code to extract the parameters at the top of your script. Also in your for loop instead of looping on @ARGV, you would instead loop on the array in your querystring.

# at the top to load your parameters
# call the script as script.pl?zipName=blah&members=abc&members=xyz
my $zipName = $cgi->param('zipName');
my @members = $cgi->param('members');

print 'usage message' unless $zipName and @members
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integral, resident of freenode's #perl