I thought floating point numbers were the computer form of real numbers,
ie. they have a decimal point but 1000000000000000000000000000001 is an integer.
Numbers are always floating-point in perl. Usually. True, you can use integer, but that doesn't seem to take effect until after the parser has chewed the number up and spat it out as a float. On many platforms, 1000000000000000000000000000001 is too big a number to represent as an integer, anyway. Integers have some implementation-dependent maximum number of bits. Computer arithmetic is not the same as mathematical arithmetic. There's always some limit on the size (number of digits) of a number the computer can remember, even if it's the machine's entire virtual memory area.