Shell function parameters pass-by-reference

[John Chludzinski]

As is probably no surprise to anyone, the script below results in: P = 0

   #!/usr/bin/ksh

   P=0
   function test
   {
     $1=12
   }
   test P
   echo "P = $P"

   exit 0

Is there a way to pass-by-reference?  Where P = 12 ?

---John