build.sbt

import Dependencies._

ThisBuild / scalaVersion := "2.13.6"
ThisBuild / version := "0.1.0-SNAPSHOT"
ThisBuild / organization := "com.example"
ThisBuild / organizationName := "example"

lazy val root = (project in file("."))
  .settings(
    name := "Scala Seed Project",
    libraryDependencies ++= Seq(
      scalaTest % Test,
      "org.scala-lang.modules" %% "scala-xml" % "2.0.1"
    )
  )

// See https://www.scala-sbt.org/1.x/docs/Using-Sonatype.html for instructions on how to publish to Sonatype.

Main.scala

package example

import scala.xml._
import scala.xml.transform._

object Hello extends App {
  val xml = """
    |<root>
    |<p><a href="http://[email protected]">abc</a></p>
    |<p><a href="http://foo.com">abc</a></p>
    |<h1>
    | <p><a href="http://[email protected]">abc</a></p>
    |</h1>
    |</root>
  """.stripMargin

  val rule = new RuleTransformer(new RewriteRule {
    override def transform(n: Node): NodeSeq = n match {
      case e: Elem if (e \\ "p" \\ "a" \@ "href").contains("@") =>
        <p>{(e \\ "p" \ "a").text}</p>
      case _ => n
    }
  })

  println(rule.transform(XML.loadString(xml)))
  //<root>
  //<p>abc</p>
  //<p><a href="http://foo.com">abc</a></p>
  //<h1>
  // <p>abc</p>
  //</h1>
  //</root>
}

abcefghi