You know, I saw your script and immediately thought about cleaning it up. I didn't even think about reading your question :)

A simple way of ensuring that only one option is used at a time:

GetOptions(
    'add=s'  =>\my $add,
    'edit=s' =>\my $edit,
    'list=s' =>\my $list,
    'view=s' =>\my $view,
    'man'    => sub {pod2usage({-verbose => 2, -input => \*DATA}); exi
+t},
    'help|?' => sub {pod2usage({-verbose => 1, -input => \*DATA}); exi
+t},
);

if (1 == grep { defined } ( $add, $edit, $list, $view )) {
    print "Good!";
}
else {
    print "Bad!\n";
}
[download]