Kwargs(3) Simple, clean handing of named/keyword arguments.


version 0.01


use Kwargs;
# just named
my ($foo, $bar, baz) = kw @_, qw(foo bar baz);
# positional followed by named
my ($pos, $opt_one, $opt_two) = kwn @_, 1, qw(opt_one opt_two)
# just a hashref
my $opts = kw @_;
# positional then hashref
my ($one, $two, $opts) = kwn @_, 2;


Named arguments are good, especially when you take lots of (sometimes optional) arguments. There are two styles of passing named arguments (by convention) in perl though, with and without braces:

    sub foo {
        my $args = shift;
        my $bar  = $args->{bar};
    foo({ bar => 'baz' });
    sub bar {
        my %args = @_;
        my $foo  = $args{foo};
    bar(foo => 'baz');

If you want to support both calling styles (because it should be mainly a style issue), then you have to do something like this:

    sub foo {
        my $args = ref $_[0] eq 'HASH' ? $_[0] : { @_ };
        my $bar  = $args->{bar};

Which is annoying, and not even entirely correct. What if someone wanted to pass in a tied object for their optional arguments? That could work, but what are the right semantics for checking for it? It also gets uglier if you want to unpack your keyword arguments in one line for clarity:

    sub foo {
        my ($one, $two, $three) = 
            @{ ref $_[0] eq 'HASH' ? $_[0] : { @_ } }{qw(one two three) };

Did I say clarity? HAHAHAHAHA! Surely no one would actually put something like that in his code. Except I found myself typing this very thing, and That Is Why.


Two functions (kw and kwn) are exported by default. You can also ask for them individually or rename them to something else. See Sub::Exporter for details.

kw(@array, @names)

Short for "kwn(@array, 0, @names)"

kwn(@array, $number_of_positional_args, @names)

Conceptually shifts off n positional arguments from array, then figures out whether the rest of the array is a list of key-value pairs or a single argument (usually, but not necessarily, a hashref). If you passed in any @names, these are used as keys into the hash, and the values at those keys are appended to any positional arguments and returned. If you do not pass @names, you will get a hashref (or whatever the single argument was, like a tied object) back.

Note that if the single argument cannot be dereferenced as a hashref, this can die. No attempt is made by this module to handle the exception.


Paul Driver <[email protected]>


This software is copyright (c) 2011 by Paul Driver <[email protected]>.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.