Excellent technique. I wonder though, shouldn't that be as follows? 
sub opt_h { exists $opt{h} } # boolean
sub opt_f { exists $opt{f} ? $opt{f} : return } # takes value

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Makeshifts last the longest.

In reply to Re^2: Referencing built-ins by Aristotle
in thread Referencing built-ins by Ovid

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