The "third party" bit is hard to define as well. For example, Rust doesn't include regular expressions in the standard library, because we have made an explicit choice to keep the standard library small. But the regex package is maintained by the Rust team, so it's not _exactly_ third party. But some languages with regexes in the language just have bindings to PCRE or something similar... so it's "first party" in the sense that it's built-in, but "third party" in the sense that the code wasn't really written and isn't maintained by them.