[Bug libstdc++/61424] std::regex matches right to left, not leftmost longest

[timshen at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61424

--- Comment #2 from Tim Shen <timshen at gcc dot gnu.org> ---
Sorry, the preference of results of "|" is actually arbitrary. I'll fix it
later.