de codepoints. For example, in ASCII compatible mode, `\xFF` matches the
literal byte `\xFF`, while in Unicode mode, `\xFF` is the Unicode codepoint
`U+00FF` that matches its UTF-8 encoding of `\xC3\xBF`. Similarly for octal
notation when enabled.
6. In ASCII compatible mode, `.` matches any *byte* except for `\n`. When the
`s` flag is additionally enabled, `.` matches any byte.

# Performance

In general, one should expect performance on `&[u8]` to be roughly similar to
performance on `&str`.