code: public static Matcher<Result> startsWith(final String prefix) {
          return new Matcher<Result>() {
              @Override
              public Result matches(String input, boolean isEof) {
                  return input.startsWith(prefix)
                          ? success(input, "", prefix)
                          : failure(input, input.length() > prefix.length());
              }
  
              @Override
              public String toString() {
                  return generateToString("startsWith", prefix);
              }
          };
      }
docs: Creates a matcher that matches when the input buffer starts with the given string.
  <p/>
  If the result is successful, the {@link net.sf.expectit.Result#getBefore()} returns an
  empty string, the {@link net.sf.expectit.Result#group()} returns the given string.
  
  @param prefix the prefix string to match.
  @return the result.