When I run that code, I get
in reply to Math::BigInt Newbee question.
$ perl whomany.pl 2 675
Global symbol "$arg2" requires explicit package name at test.pl line 2
Execution of test.pl aborted due to compilation errors.
So I am guessing that the code you pasted is not the code that's actually running. You don't declare $arg2 and are missing ->new in a few places.
Also, bdiv and bmul modify inplace. I believe what you were trying to write is:
Note: Also, to be really correct, you will need to add 1 more CD to the final result to take up the remainder of the data.
#BigInt KiloByte Unit
my $KB = Math::BigInt->new( "1024" );
#BigInt MegaByte Unit
my $MB = $KB->copy()->bmul( $KB );
#BigInt GigaByte Unit
my $GB = $MB->copy()->bmul( $KB );
print "$KB, $MB, $GB\n";
my $arg1 = Math::BigInt->new( shift );
my $arg2 = Math::BigInt->new( shift );
# arg1 is in GBs
my $GBarg1 = $arg1->copy()->bmul( $GB );
# arg2 is in MBs
my $MBarg2 = $arg2->copy()->bmul( $MB );
print $GBarg1, " ", $MBarg2, "\n";
# why rc is 0?
my ($rc, $rem) = $GBarg1->copy()->bdiv( $MBarg2 );
print "rc is [$rc]\n";
Update: Clean up code a bit