Fix broken floating-point constants after setlocale for 5.38.2

[khwilliamson]

See GH #22176

---

• This set of changes requires a perldelta entry, and it is included.
• This set of changes requires a perldelta entry, and I need help writing it.
• This set of changes does not require a perldelta entry.

[khwilliamson]

I hadn't realized there was already a PR for this #22185; so I'm deferring to that