csh: how to use indirect ref to env vars

[michael <cs@networkingnewsletter.org.uk>]

Hi, I have a csh script in which I'd like to do set up a list of vars
and then to chk each of these are set, something like the below.
However, I can't find the magic incantation that allows to to check
${$Vars} eg if $InMetFiles is set on the first loop - suggestions
welcome!

#!/bin/csh
foreach Vars (InMetFiles InTerFile OutDir)
  echo Checking $Vars\.\.\.
  if ( ${?Vars} == 0) then
    echo $Vars not set \- aborting
    exit 1
  endif
end