use strict;
use warnings;

my @a1 = qw(My name is     Andrew);
my @a2 = qw(My  dog named  Andrew);

my $i = 0;
while ($a1[$i] and $a2[$i]) { # make sure something is in both arrays
    if ($a1[$i] ne $a2[$i]) {
        print "system command \$a1 $a1[$i], then for \$a2 $a2[$i]\n";
    }
    else {
        print "# \$a1 $a1[$i], and \$a2 $a2[$i] are the same\n";
    }
    $i++;
}