#!/usr/bin/perl
use strict; use warnings;
use Benchmark qw(:all);

my %h;

@h{'A'..'Z','a'..'z'} = 1..52;

sub verbose {
   my $hash = shift;
   foreach my $key (sort keys %$hash) {
      print "$key: $hash->{$key}\n";
   }
}

sub verbose2 {
   my $hash = shift;
   foreach (sort keys %$hash) {
      print "$_: $hash->{$_}\n";
   }
}

sub verbose3 {
   my $hash = shift;
   print "$_: $hash->{$_}\n" foreach sort keys %$hash;
}

sub verbose4 {
   my $hash = shift;
   print "$_: $hash->{$_}\n" for sort keys %$hash;
}

sub idiom {
   my $hash = shift;
   print map "$_: $hash->{$_}\n", sort keys %$hash;
}

cmpthese(-10, {
   'Verbose' => sub{
       local *STDOUT;
       open STDOUT, '>/dev/null' or warn "Can't open /dev/null: $!";
       verbose(\%h)
       },
   'Verbose2' => sub{
       local *STDOUT;
       open STDOUT, '>/dev/null' or warn "Can't open /dev/null: $!";
       verbose2(\%h)
       },
   'Verbose3' => sub{
       local *STDOUT;
       open STDOUT, '>/dev/null' or warn "Can't open /dev/null: $!";
       verbose3(\%h)
       },
   'Verbose4' => sub{
       local *STDOUT;
       open STDOUT, '>/dev/null' or warn "Can't open /dev/null: $!";
       verbose4(\%h)
       },
   'Idiom' => sub{
       local *STDOUT;
       open STDOUT, '>/dev/null' or warn "Can't open /dev/null: $!";
       idiom(\%h)
       },
});

##</code><code>##

Results:
            Rate    Idiom  Verbose Verbose4 Verbose3 Verbose2
Idiom    14273/s       --      -9%     -11%     -12%     -12%
Verbose  15703/s      10%       --      -2%      -3%      -3%
Verbose4 16029/s      12%       2%       --      -1%      -1%
Verbose3 16129/s      13%       3%       1%       --      -0%
Verbose2 16151/s      13%       3%       1%       0%       --