We present and illustrate Kleenex, a language for expressing general nondeterministic finite transducers, and its novel compilation to streaming string transducers with worst-case linear-time performance and sustained high throughput. Its underlying theory is based on transducer decomposition into oracle and action machines: the oracle machine performs streaming greedy disambiguation of the input; the action machine performs the output actions. In use cases Kleenex achieves consistently high throughput rates around the 1 Gbps range on stock hardware. It performs well, especially in complex use cases, in comparison to both specialized and related tools such as AWK, sed, RE2, Ragel and regular-expression libraries. Categories and Subject Descriptors D.3.1 [Formal Definitions and Theory]: Semantics; D.3.2 [Language Classifications]: Spe