Argh. If your code snippet doesn't include all the necessary imports, it's unfinished.
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TIL Tcl has a notion of 'safe interpreters', a mode where you can run untrusted code in a sandbox: https://www.tcl.tk/man/tcl8.4/TclCmd/safe.htm
Not many programming languages have this, but it's way safer to include in the implementation than try to build as a userland library.
Over a sufficiently long time horizon, all code you write is legacy code.
I've added syntax highlighting to the prompt of my programming language!
It's not strictly necessary, but it's nice to have. It caught a bug with lexing incomplete string literals too.