Regex Tester & Validator

This regex matches binary strings consisting of repeated groups where each group has zero or more `1`s optionally followed by either `01` or `0011`, ending with an optional single `0`. It accepts strings like `1`, `101`, `0011`, and `101011`, while rejecting strings containing isolated `00` (unless part of `0011`) or runs of three or more zeros. This appears to be a combinatorial pattern matching a specific counting sequence over binary alphabets.