package Foo;

sub do_something { my $i; $i++ for (1 .. 10) }

package main;
use strict;
use warnings;

use Benchmark qw( cmpthese );

my $foo = bless {}, 'Foo';

sub do_something { my $i; $i++ for (1 .. 10) }

cmpthese( -1, {
    k1 => sub { $foo->do_something },
    k2 => sub { Foo->do_something  },
    k3 => sub { Foo::do_something  },
    k4 => sub { do_something       },      
    k5 => sub { &do_something      },      
});