perl -i -pe 's/^sshd_enable=".*?"/sshd_enable="YES"/' /etc/rc.conf

##</code><code>##

perl -i -pe 's/^sshd_enable="(.*?)"/qq{sshd_enable="} . ( $1 eq "YES" ? "NO" : "YES" ) . qq{"}/e' /etc/rc.conf