./configure when run with a non-Bash /bin/sh emits an error:
checking for x86_64-pc-linux-gnu-pkg-config... /usr/sbin/x86_64-pc-linux-gnu-pkg-config
checking pkg-config is at least version 0.9.0... yes
checking for BASH_COMPLETION... yes
./configure: 3430: Bad substitution
checking that generated files are newer than configure... done
configure: creating ./config.status
[...]
./configure
when run with a non-Bash/bin/sh
emits an error:This is because the definition of TRANSFORMED_PACKAGE_NAME at https://github.com/RichiH/vcsh/blob/main/configure.ac#L108 relies on a Bashism.