eda-tools/b2/SUBST

FN=DNP { ignore }

FN=X(*) { $=$1 }

/* iteration demo */
FOO=abcde
BAR=x	/* BAR= wouldn't be syntactically correct. We need a non-empty value */
FOO=(*)(?) {
	BAR=$BAR$2
	FOO=$1
	again FOO
}
BAR=x(*) { $=$1 }	/* remove the "x" */

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

/*
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 (in pattern):
  $$
the input variable ($) can also be used as LHS for matches and assignments

  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
*/