Developer`ReplaceAllUnheld

ReplaceAllUnheld[expr, rules] applies a rule or list of rules in an attempt to transform each subpart of expr that would be automatically evaluated.

ReplaceAll operates on all subparts of an expression; ReplaceAllUnheld operates only on those subparts that would normally be evaluated.

Example: Developer`ReplaceAllUnheld[If[a, a, a], a->b] .

See also: ReplaceAll, Hold, Verbatim.