What do you mean by "nothing changes"? I'm getting different output on each run: 
#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use List::Util qw{ shuffle };


my @browsers = ('firefox', 'chrome', 'internet explorer');
my %screen = map { $_ => "$_\'s screen" } @browsers;

my @random_array = shuffle(@browsers);
for my $b1_idx (0 .. $#random_array - 1) {
  my $b1 = $screen{ $random_array[$b1_idx] };
  for my $b2_idx ($b1_idx + 1 .. $#random_array) {
      my $b2 = $screen{ $random_array[$b2_idx] };
      say "About to compare $b1 with $b2";
  }
}

[download]
About to compare firefox's screen with chrome's screen
About to compare firefox's screen with internet explorer's screen
About to compare chrome's screen with internet explorer's screen
---
About to compare chrome's screen with internet explorer's screen
About to compare chrome's screen with firefox's screen
About to compare internet explorer's screen with firefox's screen
---
About to compare internet explorer's screen with firefox's screen
About to compare internet explorer's screen with chrome's screen
About to compare firefox's screen with chrome's screen

[download]
($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

[download]

In reply to Re^7: Simplify code in Perl with "unless" conditionnal by choroba
in thread Simplify code in Perl with "unless" condition by Chaoui05

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.