Change representation of infinity

Under 5.8.9 (unfortunately, I am stuck here for a bit yet), "inf" is not a valid representation of infinity.

Fixes the following errors from testing on master:

```text
t/method.t                   (Wstat: 1024 Tests: 14 Failed: 4)
  Failed tests:  6-7, 9-10
  Non-zero exit status: 4
t/signature_error_handler.t  (Wstat: 65280 Tests: 2 Failed: 2)
  Failed tests:  1-2
  Non-zero exit status: 255
  Parse errors: No plan found in TAP output
t/too_many_args.t            (Wstat: 1024 Tests: 15 Failed: 4)
  Failed tests:  1-4
  Non-zero exit status: 4
```