gistfile1.scala

#!/usr/bin/env scala
import scala.xml._

val pattern = args(0);
val data =
  if (args.size == 2)
    XML.load(args(1));
  else
    XML.load(System.in);

def highlight(e : NodeSeq) : NodeSeq = {
  e.flatMap(_ match {
    case text : Text =>
      val highlighted = <span style="background-color: blue; color: white">{pattern}</span>
      text.data.split(pattern).map(Text(_)).flatMap(List(highlighted, _)).tail

    case elem : Elem =>
      elem.copy(child=highlight(elem.child))

    case other => other
  })
}

val newdata = data.copy(child=
  data.child.filter({
    case elem : Elem => elem.label != "body"
    case other => true
  }) ++
    highlight(data \\ "body")
);

println(newdata)