Red is a next-generation programming language strongly inspired by Rebol, but with a broader field of usage thanks to its native-code compiler, from system programming to high-level scripting and cross-platform reactive GUI, while providing modern support for concurrency, all in a zero-install, zero-config, single 1MB file! During the work on the low-level parts of the new Red lexer, the need arised for intra-function factorization abilities to keep the lexer code as DRY as possible...