in reply to Perl Golf-- testing array intersection
47 strokes with scalar returned and 45 strokes with list returned.
sub gf_intersector { # 1 2 3 4 #2345678901234567890123456789012345678901234567 0+grep${{map{$_,1}@y}}{$_},keys%{{map{$_,1}@x}} } [download]