For the sake of exhaustivity, let's point out that numeric literals in Perl6 separate rationals (Rat) and floating-point numbers (Num), which means the first Perl6 example would work as intended provided we stick with Rat:

  > 123456789 - 0.0000001
  123456788.9999999
  > (123456789 - 0.1) - 123456789
  -0.1

Rationals represent numbers of the form a÷b, with a a bigint and b a 64-bit integer. When b gets too big for that fast representation, it gets converted to a Num (ie, IEEE 754).

  > (1 / (10 ** 100)).WHAT
  (Num)

That tradeoff is reasonable, as numbers that cannot be represented this way are very likely to be non-rational math (eg, sqrt, exp, sin, pi, that kind of thing). For money, this is safe. For real numbers, well:

  > sin(0).WHAT
  (Num)

FatRat uses a bigint for b. Obviously, it still cannot accurately represent non-rational numbers such as pi.

Reference: https://docs.perl6.org/language/syntax#Number_literals https://docs.perl6.org/type/Rat