Please Note: Portable as in portableapps.com, not in the traditional sense of a language that can be used on multiple architectures or operating systems. Whoeve
For tcl, apart from Tclkit, freewrap is another small portable, self-contained interpreter for tcl.
Just rename the freewrap executable to something else will convert it to a stand-alone interpreter. Renaming it back to freewrap will convert it to a script wrapper.
Also, freewrapped apps contain a tcl interpreter. In dire emergencies you can try opening the app as a zip file and edit/replace the tcl code contained within (just remember to make a copy first). This has saved me several times when I'm at a client site without development tools but need to troubleshoot something. I just make a copy of one of my deployed app and presto - instant development environment!