Devel::PartialDump - Partial dumping of data structures, optimized for argument printing.


version 0.20


    use Devel::PartialDump;

    sub foo {
        print "foo called with args: " . Devel::PartialDump->new->dump(@_);

    use Devel::PartialDump qw(warn);

    # warn is overloaded to create a concise dump instead of stringifying $some_bad_data
    warn "this made a boo boo: ", $some_bad_data


This module is a data dumper optimized for logging of arbitrary parameters.

It attempts to truncate overly verbose data, in a way that is hopefully more useful for diagnostics warnings than

    warn Dumper(@stuff);

Unlike other data dumping modules there are no attempts at correctness or cross referencing, this is only meant to provide a slightly deeper look into the data in question.

There is a default recursion limit, and a default truncation of long lists, and the dump is formatted on one line (new lines in strings are escaped), to aid in readability.

You can enable it temporarily by importing functions like warn, croak etc to get more informative errors during development, or even use it as:

    BEGIN { local $@; eval "use Devel::PartialDump qw(...)" }

to get DWIM formatting only if it's installed, without introducing a dependency.


"foo" => "bar"
    foo: "bar"
foo => "bar", gorch => [ 1, "bah" ]
    foo: "bar", gorch: [ 1, "bah" ]
[ { foo => ["bar"] } ]
    [ { foo: ARRAY(0x9b265d0) } ]
[ 1 .. 10 ]
    [ 1, 2, 3, 4, 5, 6, ... ]
"foo" . chr(1)



The maximum character length of the dump.

Anything bigger than this will be truncated.

Not defined by default.


The maximum number of elements (array elements or pairs in a hash) to print.

Defaults to 6.


The maximum level of recursion.

Defaults to 2.


Whether or not to let objects stringify themselves, instead of using "StrVal" in overload to avoid side effects.

Defaults to false (no overloading).


Whether or not to autodetect named args as pairs in the main dump function. If this attribute is true, and the top level value list is even sized, and every odd element is not a reference, then it will dumped as pairs instead of a list.


All exports are optional, nothing is exported by default.

This module uses Sub::Exporter, so exports can be renamed, curried, etc.


See the various methods for behavior documentation.

These methods will use $Devel::PartialDump::default_dumper as the invocant if the first argument is not blessed and isa Devel::PartialDump, so they can be used as functions too.

Particularly warn can be used as a drop in replacement for the built in warn:

    warn "blah blah: ", $some_data;

by importing

    use Devel::PartialDump qw(warn);

$some_data will be have some of it's data dumped.


The default dumper object to use for export style calls.

Can be assigned to to alter behavior globally.

This is generally useful when using the warn export as a drop in replacement for CORE::warn.


warn @blah

A wrapper for dump that prints strings plainly.

show @blah
show_scalar $x

Like warn, but instead of returning the value from warn it returns its arguments, so it can be used in the middle of an expression.

Note that

    my $x = show foo();

will actually evaluate foo in list context, so if you only want to dump a single element and retain scalar context use

    my $x = show_scalar foo();

which has a prototype of $ (as opposed to taking a list).

This is similar to the venerable Ingy's fabulous and amazing XXX module.


Drop in replacements for Carp exports, that format their arguments like warn.

dump @stuff

Returns a one line, human readable, concise dump of @stuff.

If called in void context, will warn with the dump.

Truncates the dump according to max_length if specified.

dump_as_list $depth, @stuff
dump_as_pairs $depth, @stuff

Dump @stuff using the various formatting functions.

Dump as pairs returns comma delimited pairs with => between the key and the value.

Dump as list returns a comma delimited dump of the values.

format $depth, $value
format_key $depth, $key
format_object $depth, $object
format_ref $depth, $Ref
format_array $depth, $array_ref
format_hash $depth, $hash_ref
format_undef $depth, undef
format_string $depth, $string
format_number $depth, $number
quote $string

The various formatting methods.

You can override these to provide a custom format.

format_array and format_hash recurse with $depth + 1 into dump_as_list and dump_as_pairs respectively.

format_ref delegates to format_array and format_hash and does the max_depth tracking. It will simply stringify the ref if the recursion limit has been reached.


Bugs may be submitted through the RT bug tracker (or

There is also a mailing list available for users of this distribution, at

There is also an irc channel available for users of this distribution, at #moose on


יובל קוג'מן (Yuval Kogman) <>


  • Karen Etheridge <>

  • Florian Ragwitz <>

  • Steven Lee <>

  • Leo Lapworth <web@web-teams-computer.local>

  • Jesse Luehrs <>

  • David Golden <>

  • Paul Howarth <>


This software is copyright (c) 2008 by יובל קוג'מן (Yuval Kogman).

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