# in you declaration at the beginnning of the script
# or in an ini file
%urlsForOccassions{
'fat' => 'weightwatchers.com',
'skinny' => 'muscle.com'
};

# in your script somewhere
$urls .= $urlsForOccassions{'fat'} if $fat;
$urls .= $urlsForOccassions{'skinny'} if $skinny;
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just as my 0.02

Have a nice day
All decision is left to your taste
Update
You can also then populate the hash from a CSV file or a DB to make it even more easy to maintain for nonprogrammers