++ed by:

6 PAUSE users
6 non-PAUSE users.

Dave Rolsky
and 2 contributors


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


version 0.27


    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 true, 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 values. The params you pass must be a arrayref of key-value pairs. The order of these pairs determines the order in which values are returned.

    You cannot combine slurpy with named_to_list as there is no way to know how to order the extra return values.


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 the following additional parameters:

  • 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.

    This name will also be used in some exception messages, even if Sub::Util is not available.

    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.

  • debug

    Sets the EVAL_CLOSURE_PRINT_SOURCE environment variable to true before calling Eval::Closure::eval_closure(). This causes the source of the subroutine to be printed before it's eval'd.


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>

  • Gregory Oschwald <oschwald@gmail.com>

  • Tomasz Konojacki <me@xenu.pl>


This software is Copyright (c) 2016 - 2018 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.