open(FILE, "<", "Q.txt");

##</code><code>##

        while($number <= $#column) {       #go through the array from 0 to the last element
                   $number++;
                 }

##</code><code>##

for my $element (@array_name) {
    # Do something with $element here
}

##</code><code>##

for my $index (0 .. $#array_name) {
    # Do something with $index here
}