devd rule wierd output

[Nikos Vassiliadis]

Hi,

I have this in my devd rules:
> notify 10 {
>         match "system"          "ZFS";
>         match "type"            "misc.fs.zfs.scrub_start";
>         action "touch /var/run/scrub_$pool_name; logger -t ZFS 'zpool $pool_name started scrubbing'";
> };

While this is working OK on FreeBSD-10, on FreeBSD-12 I noticed that
$pool_name is different. FreeBSD-10:
Sep  5 20:35:56 clio ZFS: zpool clio started scrubbing
FreeBSD-12:
Sep  5 20:47:35 aurora ZFS[1302]: zpool $aurora-os started scrubbing

While it assigns the value, it weirdly includes a dollar sign
at the front.

Thoughts?
Should I open a PR?

Nikos