Tcl is a cross platform language with full unicode support.
Flexibility: redefine or enhance existing commands or write new commands.
Event driven programming: Event driven I/O and variable tracing.
Library Interface: It is very easy to integrate existing C libraries into Tcl and provide a Tcl interface to the C library. These interface “stubs” are not tied to any particular version of Tcl and will continue to work even after upgrading Tcl.
Tcl Interface: Tcl provides a complete API so you use the Tcl interpreter from within your C/Python/Ruby/Java/R program.