Perlで動的ディスパッチ/動的メソッド定義

gistfile1.pl

use strict;
use warnings;

# http://d.hatena.ne.jp/yuheiomori0718/20120116/1326715412

package MyString;

use overload q{""} => \&as_string, fallback => 1;

sub new {
    my ($class, $str) = @_;
    return bless \$str, $class;
}

sub as_string { ${$_[0]} }

my %colors = (
    black   => '000',
    red     => 'f00',
    green   => '0f0',
    yellow  => 'ff0',
    blue    => '00f',
    magenta => 'f0f',
    cyan    => '0ff',
    white   => 'fff',
);

for my $color (keys %colors) {
    my $code = $colors{$color};
    no strict 'refs';
    *{__PACKAGE__ . '::' . "in_$color"} = sub {
        my $self = shift;
        return qq{<span style="color: #$code">$self</span>};
    };
}

package main;

my $str = MyString->new('Hello, world!');
my $method_to_call = 'in_black';
print $str->$method_to_call;