G'day perlvroom,

This does what you want:

#!/usr/bin/env perl

use strict;
use warnings;
use Data::Dump;

my %hash = ('a' => ['1', '2'], 'b' => ['2', '3'], 'c' => ['1', '2']);
dd \%hash;
my %seen; 
$seen{join $; => @{$hash{$_}}}++ and delete $hash{$_} for keys %hash;
dd \%hash;
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Output:

{ a => [1, 2], b => [2, 3], c => [1, 2] }
{ a => [1, 2], b => [2, 3] }
[download]

You can use whatever you want as the join separator. I've used $; as it's probably unlikely to occur in your arrayref data; obviously, you'll have a better idea of this than me. It used to be used in Perl4 to emulate multidimensional arrays but it's rarely seen in Perl5 code: I occasionally find it useful in this sort of situation. Read about it in perlvar (aka $SUBSCRIPT_SEPARATOR and $SUBSEP).