``?``

Matches one non-separator character.

``[seq]``

Matches one character in *seq*.

Matches one character in *seq*, where *seq* is a sequence of characters.

Range expressions are supported; for example, ``[a-z]`` matches any lowercase ASCII letter.

Multiple ranges can be combined: ``[a-zA-Z0-9_]`` matches any ASCII letter, digit, or underscore.

``[!seq]``

Matches one character not in *seq*.

Matches one character not in *seq*, where *seq* follows the same rules as above.

For a literal match, wrap the meta-characters in brackets.

For example, ``"[?]"`` matches the character ``"?"``.