Perlでサブルーチンプロトタイプ宣言を行う

Params::Validate使えば出来るよ！
プロトタイプ宣言して、型がおかしければ例外発生させてくれます。

test_params_validate.pl

  6 package TestClass;
  7 
  8 use Params::Validate qw/:all/;
  9 use Data::Dumper;
 10 
 11 sub new {
 12   my $self = bless {}, shift;
 13   my %args =
 14   validate(@_, { name   => { type    => SCALAR     },
 15                  skills => { type    => ARRAYREF,
 16                              default => ["Banter"] },
 17                  age    => { type    => SCALAR     },
 18                  hair   => { type     => SCALAR,
 19                              optional => 1         },
 20              });
 21   #if ($!) {
 22   #  print "error:", $!, $/;
 23   #}
 24   return $self;
 25 }
 26 
 27 1;
 28 
 29 package main;
 30 
 31 use Data::Dumper;
 32 
 33 my $faith = TestClass->new(
 34   name => "Faith",
 35   age  => "17",
 36   hair => [1,2,3],
 37 );
 38 print Dumper($faith), $/;
 39 
 40 1;

これを、実行すると

[yuki@sorauta web]$ perl docs/test_params_validate.pl
The 'hair' parameter ("ARRAY(0x1a3812a0)") to TestClass::new was an 'arrayref', which is not one of the allowed types: scalar
at /usr/lib/perl5/site_perl/5.8.8/Params/ValidatePP.pm line 630
Params::Validate::__ANON__('The \'hair\' parameter ("ARRAY(0x1a3812a0)") to TestClass::ne...') called at /usr/lib/perl5/site_perl/5.8.8/Params/ValidatePP.pm line 484
Params::Validate::_validate_one_param('ARRAY(0x1a3812a0)', 'HASH(0x1a57aea0)', 'HASH(0x1a568460)', 'The \'hair\' parameter ("ARRAY(0x1a3812a0)")') called at /usr/lib/perl5/site_perl/5.8.8/Params/ValidatePP.pm line 353
Params::Validate::validate('ARRAY(0x1a507910)', 'HASH(0x1a57ae40)') called at docs/test_params_validate.pl line 13
TestClass::new('undef', 'name', 'Faith', 'age', 17, 'hair', 'ARRAY(0x1a3812a0)') called at docs/test_params_validate.pl line 33

こんなふーに怒ってくれます！
やったね！