The regex code does not work with multibyte codesets like UTF-8.
In fact, it doesn't even work with single-byte codesets like ISO-8859-1.
The comparison blows up at index 128 (the range is 0 to UCHAR_MAX (255).

As a temporary workaround, all comparisons will be done in C locale
regardless of the environment setting. The regex library needs to be
updated to handle all codesets.

Obtained from: Dragonfly