To do regex matching efficiently, you need to compile the pattern before using it. That'd exclude dynamically "calling" other regex patterns. But bigger regex pattern strings can be composed from smaller regex pattern strings. You'd just need to do the composition before the compilation.

Swift has a RegexBuilder[1][2] interface, in addition to the usual string-ey interface that allows composition.

[1]: https://github.com/swiftlang/swift-evolution/blob/main/propo...

[2]: https://developer.apple.com/documentation/regexbuilder