I show another way to solve the problem: to modify the original code using bash.
make one single shellscript
put a shebang at the top, #!/bin/bash, to control which shell should run the script
make a ...
From the comment:
But the script uses set -Eeo pipefail
set -e causes the whole script to fail if and when sha256sum --check exits with a falsy status. To avoid that, put the command in any sort of ...
ln -sf -- /'path to theme file' $argv[-1]/interface-theme
Where the n glob qualifier enables numericglobsort (where 3.10 sorts after 3.9 instead of between 3.1 and ...