sub in_common {
	my $all = join '', scalar( reverse $_[ 0 ] ), @_[ 1 .. $#_ ];
	my $offs = length $_[ 0 ];
	my $minpos = 0;
	return grep {
		my $pos = index( $all, $_, $offs-- );
		$pos >= $minpos++;
	} split //, $_[ 0 ];
}