Enter one finite regex per line and expand its alternations into individual strings.
(a|b),
nested groups,
?,
empty alternatives,
(?:...),
character classes such as [abc],
escaped literals such as \.,
and bounded quantifiers such as {2,4}.
^ and $ are treated as zero-width
assertions and therefore aren't included in the output.
*, +, and unrestricted
{n,} are rejected because they have infinitely many expansions.