UNIX shell script is not a unique language but a collection of dialects that share a common syntax base. Each interpreter, like Bash, Zsh or Dash adds several features which are not present in other interpreters.
It is quite difficult to write a complex (and long) shell script without using one of this specific features.
The parser and usage code generated by the build-shellscript is compatible with:
There is no plan to make the UNIX shell parser compatible with other interpreters in the near future.