REF=R[0-9]* {
	T=R
	VAL=(#R) { R=$1 }
	TOL = 5%
	FN=*% { TOL=$$ }
	break REF
//	end break again
}

/*
pattern:
  () |  like in RE
  * ?   like in glob
  (#U)  expect a numeric value of unit U (use substring to get canonical value)

subst:  $1 ... $field

substring:
  $1, $2, ...
variable:
  $foo, ...
with curly braces:
  ${foo}, ...
input variable:
  $$

  Caveat:

  Wrong: FN=* { X=$FN }		there is no variable called FN
  Right: FN=* { X=$$ }		yields the Fn field selected by FN

  Wrong: VAL=(#R) { R=$VAL }	yields literal value
  Wrong: VAL=(#R) { R=$$ }	yields literal value
  Right: VAL=(#R) { R=$1 }	yield canonicalized value
*/