If you're wanting to ensure they only use one option, it seems the easiest would be to only allow one option. For example:

GetOptions(
           'request|r=s' =>\$Request,
           'man|m'     =>\$Manual,
           'help|h|?'  =>\$Help
          );

if ($Request =~ /^list$/i)
{
   # whatever
}
elsif ($Request =~ /^view$/i)
{
   # whatever
}
# and so  on
[download]

But I may be misunderstanding the issue. Not an uncommon event in my life.

If things get any worse, I'll have to ask you to stop helping me.