Cannot complete installation without bash

[athompso]

Stock OpenBSD 6.4 system, the only bourne shell installed out of the box is ksh (pdksh). IIRC, none of the BSDs except MacOS come with bash preinstalled. The FreeBSD instructions on the webpage show using sh instead, which works for the very first step, but the second step (source ~/perl5/perlbrew/etc/bashrc) is a non-starter without bash.