This is similar to liverpole's solution but populates the hash using a hash slice rather than a map. Also, you seem to want the resultant array sorted so I've done that.

use strict;
use warnings;

use Data::Dumper;

my @array = qw{abc def abc ghi ghi abc jklm abc def};

my %comb;
@comb{@array} = ();
my @uniq = sort keys %comb;

print Data::Dumper->Dumpxs([\@uniq], [qw{*uniq}]);
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The output is

@uniq = (
          'abc',
          'def',
          'ghi',
          'jklm'
        );
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I hope this is of use.

Cheers,

JohnGG