# within while (my $x = $count) { $count++; last if $count >= 5000000; } # without my $x; while ($x = $count) { $count++; last if $count >= 5000000; } Benchmark: timing 10 iterations of within, without... within: 40 wallclock secs (39.78 usr + 0.04 sys = 39.82 CPU) @ 0.25/s (n=10) without: 35 wallclock secs (35.09 usr + 0.00 sys = 35.09 CPU) @ 0.28/s (n=10)