use warnings;
use strict;

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

apply_mask($value, 128);
apply_mask($value,  64);
apply_mask($value,  32);
apply_mask($value,  16);
apply_mask($value,   8);
apply_mask($value,   4);
apply_mask($value,   2);
apply_mask($value,   1);

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