code: public static RegexpMatcher getMatcher( String pattern, boolean multiline ) {
        if( isJDK13() ){
           return new Perl5RegexpMatcher( pattern, true );
        }else{
           return new JdkRegexpMatcher( pattern, true );
        }
     }
docs: Returns a RegexpMatcher that works in a specific environment.<br>
  When in a JVM 1.3.1 it will return a Perl5RegexpMatcher, if the JVM is
  younger (1.4+) it will return a JdkRegexpMatcher.