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

my $i = 3;

# $i is not modified in this print statement:

print sqrt($i), $i, $i**2; #  1.7320508075688839
                           ## 1.73205080756888  3  9
                           
# $i is modified and new value of $i is used:

print sqrt($i), --$i, $i**2; #  1.7320508075688824
                             ## 1.73205080756888  2  4