use warnings;
use strict;

print "Please input a decimal no. to convert to binary : ";
chomp (my $value = <STDIN>);

foreach my $power (0..7) {
    # Originally 2 ** $power, but that's backwards!
    my $mask = 2 ** (7 - $power);
    apply_mask($value, $mask);
}


sub apply_mask {
    my $value = shift;
    my $mask  = shift;
    if ($value & $mask) {
        print "1";
    } else {
        print "0";
    }
}