my $a = "abcdefghijklmnopqrstuvwxyz"; use Benchmark; timethese(1000000, { 's1' => sub { s1($a, 5) }, 's2' => sub { s2($a, 5) }, }); sub s1 { my $a = $_[0]; $a =~ s/^.{$_[1]}//; return $a; } sub s2 { substr($_[0], $_[1]); } Results: s1: 8 wallclock secs ( 7.95 usr + 0.09 sys = 8.04 CPU) s2: 2 wallclock secs ( 2.54 usr + 0.01 sys = 2.55 CPU)