sub female { unify("ella", @_); unify("judy", @_); }; sub acts { unify("frank", @_); unify("dean", @_); unify("judy", @_); }; sub sings { unify("frank", @_); unify("dean", @_); unify("ella", @_); unify("judy", @_); }; sub person { male(@_); female(@_); }; sub actor { my ($var, $continuation) = @_; male($var, sub {acts($var, $continuation)}); }; sub actress { my ($var, $continuation) = @_; female($var, sub {acts($var, $continuation)}); };