Since the slowest version is running 646k iterations per second on my machine I think you should probably look elsewhere for ways to improve your code. I would think that the risk of using regex to modify code is not justified by such a very very minimal optimization.

Update: forgot the code the first time ;)

#!/usr/bin/perl
use strict;
use warnings;
use Benchmark 'cmpthese';

my $self = bless [123], '::main';


cmpthese( 10_000_000    , {
    normal    => sub { $self->get_value()  },
    optimized => sub { $self->get_value2() },
    direct    => sub { $self->[0] },
});


exit(0);

sub get_value {
    my $self = shift;
    return $self->[0];
}

sub get_value2 {
    $_[0]->[0];
}

__END__
C:\Perl\test>perl methods_access_599259.pl
               Rate    normal optimized    direct
normal     646454/s        --      -29%      -92%
optimized  915583/s       42%        --      -89%
direct    8532423/s     1220%      832%        --
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