You're right that probably nobody is targeting this... but also i imagine that dreamcast linux probably comes with a copy of perl and other common userland. No need to make platform specific code here. Just use a scripting language.
The SuperH is still fully supported by the GCC toolchain and is well maintained.
Also the guy behind compiler explorer, Matt Godbolt, himself was a DC developer and has added the SH architecture there as well.
https://github.com/KallistiOS/KallistiOS/commit/99c716c8915f...
use 5.010; # Or higher...
...would run. Yes, giving up on say and function signatures would be unfortunate, but Perl code tends to have very good backwards compatibility.