That's not a DSL, that's a shell script. As for what `pexp="..."` does - it's just setting the pexp variable. If you'd like to know what that does, you can just look up the bash source of `/etc/rc.d/rc.subr`, another bash script.
No DSL knowledge required, at all. Just shell knowledge, and the willingness to look at sourced shell scripts.
No DSL knowledge required, at all. Just shell knowledge, and the willingness to look at sourced shell scripts.