Question

I’m trying to create an unique array regardless of its original order and using no module, this’s what I’ve come up with so far:

my @arr = qw(b a a c d g e f);
my %hash;
@hash{@arr}=();
say keys %hash;

Answer 1

Yes. Since hash keys are unique, this is one idiomatic way to do it. The number of ways to accomplish the same thing are many.

You may also use a module, such as List::MoreUtils

use strict;
use warnings;

use List::MoreUtils qw(uniq);
print join ":", uniq qw(a a a b b c d);

Output:

a:b:c:d

Some different ways to dedupe:

my @arr = keys { map { $_ => 1 } qw(b a a c d g e f) };

The curly braces creates an anonymous hash for keys, the map statement creates a list of key/value pairs.

---

my @arr = dedupe(qw(a a b c d d e));

sub dedupe {
    my %hash = map { $_ => 1 } @_;
    return keys %hash;
}

Same thing, but in subroutine form, and split into two lines. Note that both lists will be in a semi-random order, since hashes are unordered.

The subroutine used by List::MoreUtils is equally simple, and perhaps preferable, since it will preserve the order of arguments. It still uses a hash, though.

sub uniq {
    my %seen = ();
    grep { not $seen{$_}++ } @_;
}