my $s = 'the quick brown fox'; substr($s, 10, 0) = 'light-'; # result: 'the quick light-brown fox' substr($s, -3, 0) = 'female '; # result: 'the quick light-brown female fox' substr($s, 0, 0) = 'I saw '; # result: 'I saw the quick light-brown female fox' substr($s, -0, 0) = ' cross the road'; # ' cross the road.I saw the quick light brown female fox' :(