Extending your idea a little and hopefully clarifying the points made by the other monks.

#!/bin/perl5

use strict;
use warnings;
use Data::Dumper;

my $distri;

$distri = { # hash ref
  one   => [qw{1 2 3}], # array ref
  two   => [qw{3 4 5}],
  three => [qw{6 7 8}],
};

my ($aref);

my $key_new = 'four';
$aref = [qw{9 10 11}];
$distri = update_hash($distri, $key_new, $aref);

my $key_existing = 'one';
$aref = [qw{12 13 14}];
$distri = update_hash($distri, $key_existing, $aref);

print Dumper $distri;


sub update_hash {
  
  # unpack and copy the arguments
  my ($href, $key, $aref) = @_;
  
  # key will be created if it doesn't exist
  # (autovivified)
  push @{$href->{$key}}, @{$aref}; # append
  # $href->{$key} = $aref;         # overwrite
  
  # return the copy
  # (leaving the original intact)
  return $href;
  
}

[download]
output: 
---------- Capture Output ----------
> "C:\Perl\bin\perl.exe" _new.pl
$VAR1 = {
          'three' => [
                       '6',
                       '7',
                       '8'
                     ],
          'one' => [
                     '1',
                     '2',
                     '3',
                     '12',
                     '13',
                     '14'
                   ],
          'two' => [
                     '3',
                     '4',
                     '5'
                   ],
          'four' => [
                      '9',
                      '10',
                      '11'
                    ]
        };

> Terminated with exit code 0.

[download]

In reply to Re: Function composing a hash of arrays. by wfsp
in thread Function composing a hash of arrays. by dislimit

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