#!/usr/bin/perl
use 5.018;
use strict;
use warnings;
# 1164677 

my @numbers = (15,5,7,3,9,1,20,13,9,8,15,16,2,6,12,90);
(my @newstring) = sort {$a <=> $b} @numbers;
for (@newstring) {
     print "$_ ";
}

say "\nNumber of elements: " . @newstring;               # number of elements
my $lastindex = $#newstring;
say "\$lastindex: $lastindex";
say "minus 2: " . $newstring[-2];    # "@a" provokes an "unintended interpolation" warning
say "minus 1: " . $newstring[-1];

=head output

1 2 3 5 6 7 8 9 9 12 13 15 15 16 20 90
Number of elements: 16
$lastindex: 15
minus 2: 20
minus 1: 90

=cut