I chose my words very particularly. The difference is not massive, but it is significant - i.e. it's consistently big enough to be detectable. For a very simple rw accessor closing over a single variable (that is, sub { $_[0]{$name} = $_[1] if @_ == 2; $_[0]{$name} }), it's likely to be about 10%.

For the example which would close over two variables (sub { $_[0]{$path}{$name} = $_[1] if @_ == 2; $_[0]{$path}{$name} }) it's more like 15%.

File and line number info is easy to add to stringy evals.

Moose, Moo, etc create accessors this way not just for fun, but because they're measurably faster.

use strict;
use warnings;
use Benchmark qw(cmpthese);

my $name = 'foo';
my $path = 'foobar';
my $sub1 = sub { $_[0]{$path}{$name} = $_[1] if @_ == 2; $_[0]{$path}{
+$name} };
my $sub2 = eval qq[ sub { \$_[0]{$path}{$name} = \$_[1] if \@_ == 2; \
+$_[0]{$path}{$name} } ]
    or die($@);

my $self = {};

cmpthese -1, {
    closure => sub {
        $self->$sub1(0);
        $self->$sub1( $self->$sub1 + $_ ) for 0..10_000;
    },
    stringy => sub {
        $self->$sub2(0);
        $self->$sub2( $self->$sub2 + $_ ) for 0..10_000;
    },
};

[download]
use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name

In reply to Re^4: Creating flexible method accessor (no benchmark?) by tobyink
in thread Creating flexible method accessor by puterboy

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