asterisk users - Oct 2010 - how to insert dynamic hostname into shared CDR database

So I'm in a situation where I want to consolidate cdr logs. My general
idea is to use cdr_mysql for this.

I know I can do things like
Set(CDR(userfield)=hostname)

And I can hardcode the hostname for the dialplan on each system.

But what I'd really like to do is have this dynamic, so I can use the
same exact dialplan on multiple hosts, and have hostname dynamically
generate.

I went looking for a built-in asterisk variable for this, but haven't
found anything yet.

I know I can do something like

Set(HOSTNAME=(System(/bin/hostname -s))
Set(CDR(userfield)=${HOSTNAME})

But that seems like more overhead than it should take to do this.

Can anybody think of a better way?

Hey, I just discovered

 ${SYSTEMNAME}	 * value of the systemname option of asterisk.conf

which was turned off in my asterisk.conf, but then there's an option called
autosystemname = yes

With that enabled, ${SYSTEMNAME} is giving me what I want.

I also spotted
${ENV(HOSTNAME)} which I assume would let me have whatever is set as
an environmental variable. This didn't work for me, perhaps because my
asterisk daemon is running in an environment without that variable
set?