startupitems arcanery

I am trying to understand the startupitems in the dhcp port because I want to do somewthing similar in another port. Can someone explain what the escapes, brackets, "-x", and "-r" do? And what interprets the "-x" and "-r"? The shell? startupitem.create yes startupitem.name dhcpd startupitem.init "PID=/var/run/dhcpd.pid" startupitem.start "\[ -x ${prefix}/sbin/dhcpd \] && ${prefix}/sbin/dhcpd -cf ${prefix}/etc/dhcp/dhcpd.conf -lf ${prefix}/var/db/dhcpd/dhcpd.leases" startupitem.stop "\[ -r \${PID} \] && kill \$(cat \${PID})" Mark