It's common that you want to add something to a certain Hiveconf parameter. This can be done with a command such as:
tl-config /vsmagent/xserver_args="`tl-config /vsmagent/xserver_args` -IdleTimeout=60"
This is obviously quite clumsy. It would be nive if you could write something like this instead:
Note that this is very non-trivial as a dumb concatenation of strings will likely produce the wrong result, and assuming that an initial space should always be implied is also dangerous (e.g., we have comma separated values in some places).