Depends on how you define "one-liner." Something like this might work:
{ if index($0, PATTERN) != 0 {FOUND = 1;}; if (FOUND != 0) {subst(REPLACE_THIS, WITH_THIS, $0); }
You'd want to reverse the order of the two statements if the replacement is only to occur after the pattern is found.
Cool, I'll give it a whirl tomorrow! I do want to replace all occurrences only after the keyword Thanks, jlc