This is not quite a regular expression engine

This is not quite a regular expression engine because the features currently supported are not sufficient to recognize the regular languages. For example, $\\{a^{2n} \mid n \in \mathbb N\\}$ (as a regular expression, `(aa)*`) is regular but this engine’s features cannot describe it.

The issue names no files, entry points, or tests. Start by reviewing the regex engine's supported syntax and how repetition is represented, then compare it with the `(aa)*` example. Done would require a decided scope and a tested way to recognize this regular language.

Written by the indexing model from the issue text.