print("\n\nEnter a binary number:");
chomp($binary=<STDIN>);


if ( $binary =~/\D.*/ ) { 
    print("Not a binary number!\n");
    exit;
    }


if ( $binary =~/\d.*/ ) { 

    @eachnum = split (//, $binary);
    $good = 1;
    
    foreach (@eachnum){
	    next if /0/ || /1/;
	    print("A binary number contains 1's and 0's!\n");
	    $good = 0;    
	    last;    
    }

    if ( $good == 1 ) {
           convb2d();
    }
}