% perl5.8.0
use Benchmark;

sub mychr { return pack("C", shift); }

@array = @array = (0 .. 255) x 100;

timethese(1000, {
  'sub'     => 'foreach (@array) { my $chr = chr($_) }',
  'builtin' => 'foreach (@array) { my $chr = &mychr($_) }',
  'direct'  => 'foreach (@array) { my $chr = pack("C", $_) }',
});

Benchmark: timing 1000 iterations of builtin, direct, sub...
   builtin: 156 wallclock secs (143.82 usr +  0.17 sys = 143.99 CPU) @  6.94/s (n=1000)
    direct: 53 wallclock secs (48.89 usr +  0.04 sys = 48.93 CPU) @ 20.44/s (n=1000)
       sub: 37 wallclock secs (31.16 usr +  0.03 sys = 31.19 CPU) @ 32.06/s (n=1000)