A practical language for writing analysis and transformation tools for C/C++ and other languages is provided. This language, YATL, is imperative in style and designed to be easy to use for someone familiar with the grammar of the target language. It allows the developer to describe transformations with reference to elements of the target grammar through a pluggable personality to a compiler. This provides the means for powerful, yet easy to write, transformation programs, while fundamentally remaining language agnostic.