When I initially hit this it seemed incomprehensible... then I figured out why it's happening but not yet how to fix it - so here I am humbly asking for your wisdom.

I expected the below code to create a fresh copy of @arr every time gimme() is executed. Instead it creates a new reference for @arr but reuses all of the nested references. The result is that gimme() returns the last box with its content, rather than a fresh empty box which is what I want...

I considered using Readonly or a configuration file on disk to ensure I get an empty box every time, but both seem clunky and slow. The actual data structure is nested to 5-6 levels and while it is not huge, it will be executed often.

I suspect turning the data structure into an object may be the right path, but I'm yet to pick that side of perl up... What would be your advice?

#!/usr/bin/perl -w
use strict;
use Data::Dumper;


BEGIN {
    my @arr = (
                {
                    box => {
                                attr    => {
                                            this    => 'that',
                                            foo     => 'bar',
                                           },
                                content => {}, 
                           },
                },
              );
    sub gimme {
        my @result = @arr;
        return \@result;
    }
}

my $box1_ref = gimme();
$box1_ref->[0]->{white_box}->{content}->{apples} = 5;
print "tracing: $box1_ref -> $box1_ref->[0] -> $box1_ref->[0]->{white_
+box} -> $box1_ref->[0]->{white_box}->{content}\n";
print Dumper $box1_ref->[0]->{white_box}->{content};

my $box2_ref = gimme();
print "tracing: $box2_ref -> $box2_ref->[0] -> $box2_ref->[0]->{white_
+box} -> $box2_ref->[0]->{white_box}->{content}\n";
print Dumper $box2_ref->[0]->{white_box}->{content};
[download]

Result of that code is:

tracing: ARRAY(0x20d9e70) -> HASH(0x1fcf638) -> HASH(0x20d9db0) -> HAS
+H(0x20d9de0)
$VAR1 = {
          'apples' => 5
        };
tracing: ARRAY(0x1fab0f0) -> HASH(0x1fcf638) -> HASH(0x20d9db0) -> HAS
+H(0x20d9de0)
$VAR1 = {
          'apples' => 5
        };
[download]

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.