procedure main()  # demonstrate and describe function calling syntax and semantics

   # normal procedure/function calling

   f()                      # no arguments, also command context
   f(x)                     # fixed number of arguments
   f(x,h,w)                 # variable number of arguments (varargs)
   y := f(x)                # Obtaining the returned value of a function

   # procedures as first class values and string invocation

   f!L                      # Alternate calling syntax using a list as args
   (if \x then f else g)()  # call (f or g)()
   f := write               # assign a procedure
   f("Write is now called") # ... and call it
   "f"()                    # string invocation, procedure
   "-"(1)                   # string invocation, operator

   # Co-expressions

   f{e1,e2}                 # parallel evaluation co-expression call
                            # equivalent to f([create e1, create e2])
   expr @ coexp             # transmission of a single value to a coexpression
   [e1,e2]@coexp            # ... of multiple values (list) to a coexpression
   coexp(e1,e2)             # ... same as above but only in Unicon

   # Other

   f("x:=",1,"y:=",2)       # named parameters (user defined)
end