note TimToady And indeed, you can do that in Perl too: <code> multi compress () { () } multi compress ($a) { item $a } multi compress ($x, $y, *@xs) { $x xx ($x !=== $y), compress($y, |@xs) } my @x = <a a a a b c c a a d e e e e>; say perl compress |@x; </code> 590113 590145