O' Wise ones, Can an enlightened soul tell me if the Schwartzian transform can be modified to sort uniquely items inside an arrayref while running under 'use strict'?

My code looks like this (I'm trying to sort uniquely on the field called num): 

#!/usr/local/bin/perl -w

use strict;

my $data = (
    [
        {
            num     => 'OF1234',
            title   => 'title OF1234',
        },
        {
            num     => 'AF1234',
            title   => 'title AF1234',
        },
        {
            num     => 'AF1234',
            title   => 'title AF1234',
        },
    ]
);

#print @{$data};

my @sorted =
                # now get the original array ref back
    map { $_->[0] }
                # use field 1 of anonymous array to sort (in this
                # case num)
    sort { $a->[1] cmp $b->[1] }
                # make an anonymous array of itself and num
    map { [$_, $_->{num}] }
                # start with the array ref and make it an array
    @{$data};
print join ', ', map { $_->{num} } @sorted;
print "\n";

my %saw;
undef %saw;

my @unique = grep !$saw{$_->{num}}++, @sorted;
print join ', ', map { $_->{num} } @unique;

print "\n";
exit;

[download]
which produces the desired output (first line sorted, second line unique): 
AF1234, AF1234, OF1234
AF1234, OF1234

[download]
Is there a way to get rid of the unsightly grep by using something similar to: 
my @keys = sort keys %{ { map { $_ => 1 } @array1 } };

[download]
keeping in mind that we're talking about hash data inside the arrrayref.

I can't get my hands around it. It's a wonder that I understand the Schwartzian Transform to begin with. Here's a detailed explanation of the Schwartzian at http://www.5sigma.com/perl/schwtr.html for people wanting to know more. Thanks in advance,

In reply to Can Schwartzian transform be modified to sort an arrayref uniquely? by corporate_gadfly

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