++ed by:

6 PAUSE users
7 non-PAUSE users.

Dave Rolsky
and 2 contributors


Params::ValidationCompiler - Build an optimized subroutine parameter validator once, use it forever


version 0.23


    use Types::Standard qw( Int Str );
    use Params::ValidationCompiler qw( validation_for );

        my $validator = validation_for(
            params => {
                foo => { type => Int },
                bar => {
                    type     => Str,
                    optional => 1,
                baz => {
                    type    => Int,
                    default => 42,

        sub foo {
            my %args = $validator->(@_);

        my $validator = validation_for(
            params => [
                { type => Int },
                    type     => Str,
                    optional => 1,

        sub bar {
            my ( $int, $str ) = $validator->(@_);

        my $validator = validation_for(
            params => [
                foo => { type => Int },
                bar => {
                    type     => Str,
                    optional => 1,
            named_to_list => 1,

        sub baz {
            my ( $foo, $bar ) = $validator->(@_);


This module creates a customized, highly efficient parameter checking subroutine. It can handle named or positional parameters, and can return the parameters as key/value pairs or a list of values.

In addition to type checks, it also supports parameter defaults, optional parameters, and extra "slurpy" parameters.


This module has two options exports, validation_for and source_for. Both of these subs accept the same options:

  • params

    An arrayref or hashref containing a parameter specification.

    If you pass a hashref then the generated validator sub will expect named parameters. The params value should be a hashref where the parameter names are keys and the specs are the values.

    If you pass an arrayref and named_to_list is false, the validator will expect positional params. Each element of the params arrayref should be a parameter spec.

    If you pass an arrayref and named_to_list is false, the validator will expect named params, but will return a list of values. In this case the arrayref should contain a list of key/value pairs, where parameter names are the keys and the specs are the values.

    Each spec can contain either a boolean or hashref. If the spec is a boolean, this indicates required (true) or optional (false).

    The spec hashref accepts the following keys:

    • type

      A type object. This can be a Moose type (from Moose or MooseX::Types), a Type::Tiny type, or a Specio type.

      If the type has coercions, those will always be used.

    • default

      This can either be a simple (non-reference) scalar or a subroutine reference. The sub ref will be called without any arguments (for now).

    • optional

      A boolean indicating whether or not the parameter is optional. By default, parameters are required unless you provide a default.

  • slurpy

    If this is a simple true value, then the generated subroutine accepts additional arguments not specified in params. By default, extra arguments cause an exception.

    You can also pass a type constraint here, in which case all extra arguments must be values of the specified type.

  • named_to_list

    If this is true, the generated subroutine will expect a list of key-value pairs or a hashref and it will return a list containing only the values. params must be a arrayref of key-value pairs in the order of which the values should be returned.

    You cannot combine slurpy with named_to_list as there is no way to know how the order in which extra values should be returned.


This returns a subroutine that implements the specific parameter checking. This subroutine expects to be given the parameters to validate in @_. If all the parameters are valid, it will return the validated parameters (with defaults as appropriate), either as a list of key-value pairs or as a list of just values. If any of the parameters are invalid it will throw an exception.

For validators expected named params, the generated subroutine accepts either a list of key-value pairs or a single hashref. Otherwise the validator expects a list of values.

For now, you must shift off the invocant yourself.

This subroutine accepts an additional parameter:

  • name

    If this is given, then the generated subroutine will be named using Sub::Util. This is strongly recommended as it makes it possible to distinguish different check subroutines when profiling or in stack traces.

    Note that you must install Sub::Util yourself separately, as it is not required by this distribution, in order to avoid requiring a compiler.

  • name_is_optional

    If this is true, then the name is ignored when Sub::Util is not installed. If this is false, then passing a name when Sub::Util cannot be loaded causes an exception.

    This is useful for CPAN modules where you want to set a name if you can, but you do not want to add a prerequisite on Sub::Util.


This returns a two element list. The first is a string containing the source code for the generated sub. The second is a hashref of "environment" variables to be used when generating the subroutine. These are the arguments that are passed to Eval::Closure.


Bugs may be submitted at https://github.com/houseabsolute/Params-ValidationCompiler/issues.

I am also usually active on IRC as 'autarch' on irc://irc.perl.org.


The source code repository for Params-ValidationCompiler can be found at https://github.com/houseabsolute/Params-ValidationCompiler.


If you'd like to thank me for the work I've done on this module, please consider making a "donation" to me via PayPal. I spend a lot of free time creating free software, and would appreciate any support you'd care to offer.

Please note that I am not suggesting that you must do this in order for me to continue working on this particular software. I will continue to do so, inasmuch as I have in the past, for as long as it interests me.

Similarly, a donation made in this way will probably not make me work on this software much more, unless I get so many donations that I can consider working on free software full time (let's all have a chuckle at that together).

To donate, log into PayPal and send money to autarch@urth.org, or use the button at http://www.urth.org/~autarch/fs-donation.html.


Dave Rolsky <autarch@urth.org>


  • Gregory Oschwald <goschwald@maxmind.com>

  • Tomasz Konojacki <me@xenu.pl>


This software is Copyright (c) 2016 - 2017 by Dave Rolsky.

This is free software, licensed under:

  The Artistic License 2.0 (GPL Compatible)

The full text of the license can be found in the LICENSE file included with this distribution.