'secret' function

[John Keck <jwk(at)phys.columbia.edu>]

I was trying to get from within a procedure a list of the system
variables when I stumbled across the GETHELP function that uses the
ROUTINE_NAMES function.  The latter is not described in the on-line help
or in the printed reference, so the extent of my knowledge is how the
function is used in GETHELP.

Does any one have a complete description for the use of ROUTINE_NAMES? 
If not, does anyone know how to list system variables and structures
with it?

Also, are there any other undocumented functions or procedures in IDL?

Thanks,

John