VALUE(s[,[newvalue][,selector]])

s is treated as a symbol, and if it has a value, that value is returned.
If s is not a valid symbol then an error results. Otherwise the result
is just as for a symbol appearing in a program. For compound symbols,
substitution occurs as normal, except that string constants and
expressions (types 4 and 5 in the description of symbols above) are not
allowed.

If the newvalue parameter is provided, then this value is assigned to
the symbol described above.  The symbol's old value will be returned.

If the selector is provided, then this indicates an alternative
variable pool to use instead of the REXX variable pool (except that the
word "REXX" is accepted as a valid name for the usual REXX variable
pool).  The only selector recognised by REXX/imc is the word
"ENVIRONMENT", which allows the value() function to examine and alter
environment variables.  Note that the names and values of environment
variables may not contain NUL characters.

Example: the following program

   a=1; b='*'
   c.a=1; c.b=2
   say value("a") value("c.a") value("c.b") value("d.b",6)
   say value("d.*")
   
will output "1 1 2 D.*" then give an error, because "*" is not allowed
as a component of a symbol (however "b" is, even if b="*").  The value
of d.b after executing these lines will be 6.

The instructions

   a=value("FOO","ENVIRONMENT")
   call value "FOO","bar","ENVIRONMENT"

are similar to the instructions

   a=getenv("FOO")
   call putenv "FOO=bar"

respectively.