Hence auto-tools, what do you think "./configure" is doing?
Perl is not as easy to pipe multiple commands. I wish it was, but it just isn't. Also, in the embedded space microperl might reach the system, but not perl. Also, Perl is not any better to maintain than sh, maybe Python. With BusyBox you can run a lot of scripts with a few changes.
Funny you quote Larry Wall and say Bourne should be replaced by Perl.