return scalar grep /^$who$/, @masters;

Why use a regular expression when you are looking for string equality? What would your code do if $who contained something like 'foo^bar', 'foo{2}', or 'foo[bar]' (all of which are legal IRC nicks?) I think the hash idea given by hardburn is better than a grep, but if you wanted to use grep you should probably do it something like this:

sub is_master { scalar grep $_[0] eq $_, @masters }
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sub is_master { scalar grep $_[0] eq $_, @masters and 1 }
[download]

-sauoq
"My two cents aren't worth a dime.";