*** LISTS ***

AviosPL has some usefull list processing functions, the ideas of which I have
nicked from certain other languages. First of all you must be aware that a list
in Avios is really just a string that has words/elements in it seperated by
whitespace (whitespace being any ascii code < 33 for simplicity but not 
including 0). So for example the string "hello there world" can also be
treated as a list with 3 elements in it. Elements are counted from 1 so
"hello" is element 1, "there" is 2 and "world" is 3.
   Please note that the list commands do not care how much whitespace is in
the string so "   hello   there   world   " is considered equivalent to the
previous example.

The commands which work on lists are the following:
     head, rhead, tail, rtail, insertelem, overelem, member, subelem, 
     elements, count, match & unique.

There are no addelem or mulelem commands as the string commands addstr and
mulstr can carry out the appropriate operations. To add an element to a list 
for example: 

     set list "hello there"
     :
     :
     set list [addstr list " " "world"]

Or to multply a list:
     set list "hello there "  # Need space on the end as separator
     :
     :
     set list [mulstr list 3] 
   

Please read the commands documentation to see how the list commands work.