#!/usr/bin/perl

use strict;
use warnings;

#my $number = get_number('one');
#print "$number\n";

for (qw(one two three)){
  my $number = get_number($_);
  print "$number\n";
}

{
  my $hash_ref;
  sub get_number{
    my ($num) = @_;
    unless (defined $hash_ref){
      while (<DATA>){
        chomp;
        my ($str, $num) = split /\|/;
        $hash_ref->{$str} = $num;
      }
    }
    return $hash_ref->{$num};
  }
}

__DATA__
one|1
two|2
three|3

[download]
This snippet produces the error message: 
Modification of a read-only value attempted at closure_test.pl line 19
+.

[download]
Uncomment the two lines at the top of script and the output is as expected: 
1
1
2
3

[download]
Can anyone help explain this behaviour?

Update 2

Ack! The first update was rubbish! Apologies.

Update

Deleted.

In reply to Closure producing 'Modification of read-only value' error by wfsp

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