#!perl -l

sub firstdivergence {
	my $diff = $_[0] ^ $_[1];
	$diff =~ /[^\x00]/g;
	pos $diff - 1
}

sub lastdivergence {
	my $diff = $_[0] ^ $_[1];
	$diff =~ /[^\x00]\x00*$/g;
	pos $diff - 1
}

print firstdivergence 'axcd', 'abced'; # prints 1
print lastdivergence 'axcd', 'abced';  # prints 4