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Data::Visitor::Tiny - Recursively walk data structures


version 0.001


    use Data::Visitor::Tiny;

    my $hoh = {
        a => { b => 1, c => 2 },
        d => { e => 3, f => 4 },

    # print leaf (non-ref) values on separate lines (1 2 3 4)
    visit( $hoh, sub { return if ref; say } );

    # transform leaf value for a given key
        sub {
            my ( $key, $valueref ) = @_;
            $$valueref = "replaced" if $key eq 'e';
    say $hoh->{d}{e}; # "replaced"


This module provides a simple framework for recursively iterating over a data structure of hashrefs and/or arrayrefs.



    visit( $ref, sub { ... } );

The visit function takes a hashref or arrayref and recursively visits all values via pre-order traversal, calling the provided callback for each value. Only hashrefs and arrayrefs are traversed; objects, even if they override hash or array dereference, are only ever treated as values. Hash keys are sorted lexicographically before iteration, ensuring consistent visitation order in the face of Perl's hash order randomization.

Within the callback, the $_ variable is set to the value of the node. The callback also receives three arguments: $key, $valueref, and $context. The $key is the hash key or array index of the value. The $valueref is a scalar reference to the value; use it to modify the value in place. The $context is a hashref for tracking state throughout the visiting process. Context keys beginning with '_' are reserved for Data::Visitor::Tiny; you may store whatever other keys/values you need. The only key provided currently is _depth, which starts at 0 and reflects how deep the visitor has recursed.

The visit function returns the context object.



Bugs / Feature Requests

Please report any bugs or feature requests through the issue tracker at You will be notified automatically of any progress on your issue.

Source Code

This is open source software. The code repository is available for public review and contribution under the terms of the license.

  git clone


David Golden <>


This software is Copyright (c) 2018 by David Golden.

This is free software, licensed under:

  The Apache License, Version 2.0, January 2004