- Tcl (pronounced as an acronym, /ˈtɪk(ə)l/, like tickle, or as an initialism, /ˌtiːˌsiːˈɛl/, like T-C-L; originally Tool Command Language) is a high-level, general-purpose, interpreted, dynamic programming language. It was designed with the goal of being very simple but powerful. Tcl casts everything into the mold of a command, even programming constructs like variable assignment and procedure definition. Tcl supports multiple programming paradigms, including object-oriented, imperative, functional, and procedural styles.