perl -le '@x = qw(a b c d e f); @y = qw(a d f); $n = grep { $e = $_; not grep { $e =~ /\Q$_/i } @x } @y; print "Count of elements in (@y) that are NOT present in (@x) = $n" ' Count of elements in (a d f) that are NOT present in (a b c d e f) = 0