Shell Programming and Scripting

use warnings;
use strict;
my $i;
$i=0;
while ($i=0)
{
        print "Welcome to an interactive Perl program. Enter either q or Q to terminate the program or c to continue. Enter your key now: ";
        my $input;
        $input = <STDIN>;
        if (($input ne "q") || ($input ne "Q") || ($input ne "c"))
        {
                print "Welcome to an interactive Perl program. Enter either q or Q to terminate the program or c to continue. Enter your key now: ";
        }
        elsif (($input eq "q") || ($input eq "Q"))
        {
                exit;
        }
        else
        {
                print "Please enter one x coordinate: ";
                my $x1;
                $x1 = <STDIN>;
                print "Please enter one y coordinate: ";
                my $y1;
                $y1 = <STDIN>;
                print "Please enter one z coordinate: ";
                my $z1;
                $z1 = <STDIN>;
                print "Please enter a second x coordinate: ";
                my $x2;
                $x2 = <STDIN>;
                print "Please enter a second y coordinate: ";
                my $y2;
                $y2 = <STDIN>;
                print "Please enter a second z coordinate: ";
                my $z2;
                $z2 = <STDIN>;
        }
}

while ($i==0)