A really quick way to do it is to create a hash, using the elements of the array as keys.

The keys of a hash are always unique, so you just have to reconstruct the list of keys at the end:

use strict;
use warnings;

my @array  = ("abc","def","abc","ghi","ghi","abc","jklm","abc","def");
my %hash   = map { $_ => 1 } @array;
my @unique = keys %hash;
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