Get the first item of the list returned by function

A simple simulation of the problem:

use strict;
use warnings;

sub uniq
{
  my %seen;
  grep !$seen{$_}++, @_;
}

my @a = (1, 2, 3, 1, 2);

print shift @{uniq(@a)}; 

Can’t use string ("3") as an ARRAY ref while "strict refs" in use

>Solution :

Need to impose a list context on the function call, and then pick the first element from the list.

The print, or any other subroutine call, already supplies a list context. Then one way to extract an element from a list

print +( func(@ary) )[0];

This disregards the rest of the list.

That + is necessary (try without it), unless we use another set of parens, that is

print( (func(@ary))[0] );