On FreeBSD, perl defaults to installation in /usr/local/bin/perl since it is not a part of the base system. If the option to create symlinks in /usr/bin is not selected, > building and running ikiwiki will fail because the shebang lines use #!/usr/bin/perl [args]. Changing this to #!/usr/bin/env -S perl [args] fixes the issue.

I think this should be a concern of ikiwiki's official FreeBSD port.

At any rate, even if it is decided that ikiwiki should be fixed, then it is probably better to use $installbin/perl from -MConfig and not the env hack.