Below is the code. I tried different lengths of strings (upper bound in 1..10000) and number of iterations (first argument to timethese).
#!/usr/bin/perl
use strict;
use warnings;
use Benchmark qw/cmpthese timethese/;
my $y = join "", 1..10000;
my %tr;
@tr{map chr, 0..255} = map chr, 1..255,0;
my $tr = eval 'sub {$_[0] =~ tr/\x00-\xff/\x01-\xff\x00/r}';
my $trans = sub
{
my $x = $y;
$x =~ tr/\x00-\xff/\x01-\xff\x00/r;
};
my $subst = sub
{
my $x = $y;
$x =~ s/(.)/$tr{$1}/egr;
};
my $eval = sub
{
my $x = $y;
eval '$x =~ tr/\x00-\xff/\x01-\xff\x00/r';
};
my $preceval = sub
{
my $x = $y;
&$tr($x);
};
my $z = &$trans;
$z eq &$subst or die;
$z eq &$eval or die;
$z eq &$preceval or die;
length($y) == length($z) or die;
printf "length: %s\n", length($y);
timethese(0, {
trans => $trans,
subst => $subst,
eval => $eval,
preceval => $preceval,
});
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