From Tapestries MUCK
This takes a property based list, and concatenates all its lines together, stripping spaces from the beginning and end of each one. It then evaluates the result for MPI commands, and returns the resulting string.
A property based list is a series of properties that are consecutively numbered. The server understands several different formats, and can also read in property lists in either the propnameX format, or the propname#/X format.
If no obj argument is supplied, then it looks for the list somewhere down the environment from the trigger object. Otherwise, it looks for the list down the environment from the given object.