Perinci::Sub::Util - Helper when writing functions


This document describes version 0.42 of Perinci::Sub::Util (from Perl distribution Perinci-Sub-Util), released on 2015-09-04.


Example for err() and caller():

 use Perinci::Sub::Util qw(err caller);

 sub foo {
     my %args = @_;
     my $res;

     my $caller = caller();

     $res = bar(...);
     return err($err, 500, "Can't foo") if $res->[0] != 200;

     [200, "OK"];

Example for gen_modified_sub():

 use Perinci::Sub::Util qw(gen_modified_sub);

 $SPEC{list_users} = {
     v => 1.1,
     args => {
         search => {},
         is_suspended => {},
 sub list_users { ... }

     output_name => 'list_suspended_users',
     base_name   => 'list_users',
     remove_args => ['is_suspended'],
     output_code => sub {
         list_users(@_, is_suspended=>1);

Example for die_err() and warn_err():

 use Perinci::Sub::Util qw(warn_err die_err);
 warn_err(403, "Forbidden");
 die_err(403, "Forbidden");


What if I want to put result ($res->[2]) into my result with err()?

You can do something like this:

 my $err = err(...) if ERROR_CONDITION;
 $err->[2] = SOME_RESULT;
 return $err;




gen_modified_sub(%args) -> [status, msg, result, meta]

Generate modified metadata (and subroutine) based on another.

Often you'll want to create another sub (and its metadata) based on another, but with some modifications, e.g. add/remove/rename some arguments, change summary, add/remove some properties, and so on.

Instead of cloning the Rinci metadata and modify it manually yourself, this routine provides some shortcuts.

You can specify base sub/metadata using base_name (string, subroutine name, either qualified or not) or base_code (coderef) + base_meta (hash).

Arguments ('*' denotes required arguments):

  • add_args => hash

    Arguments to add.

  • base_code => code

    Base subroutine code.

    If you specify this, you'll also need to specify base_meta.

    Alternatively, you can specify base_name instead, to let this routine search the base subroutine from existing Perl package.

  • base_meta => hash

    Base Rinci metadata.

  • base_name => str

    Subroutine name (either qualified or not).

    If not qualified with package name, will be searched in the caller's package. Rinci metadata will be searched in %SPEC package variable.

    Alternatively, you can also specify base_code and base_meta.

  • description => str

    Description for the mod subroutine.

  • install_sub => bool (default: 1)

  • modify_args => hash

    Arguments to modify.

    For each argument you can specify a coderef. The coderef will receive the argument ($arg_spec) and is expected to modify the argument specification.

  • modify_meta => code

    Specify code to modify metadata.

    Code will be called with arguments ($meta) where $meta is the cloned Rinci metadata.

  • output_code => code

    Code for the modified sub.

    If not specified will use base_code (which will then be required).

  • output_name => str

    Where to install the modified sub.

    Subroutine will be put in the specified name. If the name is not qualified with package name, will use caller's package. If no output_code is specified, the base subroutine reference will be assigned here.

    Note that this argument is optional.

  • remove_args => array

    List of arguments to remove.

  • rename_args => hash

    Arguments to rename.

  • replace_args => hash

    Arguments to add.

  • summary => str

    Summary for the mod subroutine.

Returns an enveloped result (an array).

First element (status) is an integer containing HTTP status code (200 means OK, 4xx caller error, 5xx function error). Second element (msg) is a string containing error message, or 'OK' if status is 200. Third element (result) is optional, the actual result. Fourth element (meta) is called result metadata and is optional, a hash that contains extra information.

Return value: (hash)

caller([ $n ])

Just like Perl's builtin caller(), except that this one will ignore wrapper code in the call stack. You should use this if your code is potentially wrapped. See Perinci::Sub::Wrapper for more details.

err(...) => ARRAY


Generate an enveloped error response (see Rinci::function). Can accept arguments in an unordered fashion, by utilizing the fact that status codes are always integers, messages are strings, result metadata are hashes, and previous error responses are arrays. Error responses also seldom contain actual result. Status code defaults to 500, status message will default to "FUNC failed". This function will also fill the information in the logs result metadata.


 err();    # => [500, "FUNC failed", undef, {...}];
 err(404); # => [404, "FUNC failed", undef, {...}];
 err(404, "Not found"); # => [404, "Not found", ...]
 err("Not found", 404); # => [404, "Not found", ...]; # order doesn't matter
 err([404, "Prev error"]); # => [500, "FUNC failed", undef,
                           #     {logs=>[...], prev=>[404, "Prev error"]}]

Will put stack_trace in logs only if Carp::Always module is loaded.


This is a shortcut for:

 $res = err(...);
 warn "ERROR $res->[0]: $res->[1]";


This is a shortcut for:

 $res = err(...);
 die "ERROR $res->[0]: $res->[1]";


Please visit the project's homepage at


Source repository is at


Please report any bugs or feature requests on the bugtracker website

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.


perlancar <>


This software is copyright (c) 2015 by

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