Using StringBuffer to add backclash to an String

 OpCode.java:
 字母、数字、下划线:
  static final boolean _isWordCharacter(char token) {
    return (Character.isLetterOrDigit(token) || token == '_');
  }

Perl5Compile.java
  public static final String quotemeta(char[] expression) {
    int ch;
    StringBuffer buffer;
    buffer = new StringBuffer(2*expression.length);
    for(ch = 0; ch < expression.length; ch++) {
      if(!OpCode._isWordCharacter(expression[ch]))
      buffer.append('\\');
         buffer.append(expression[ch]);
    }
    return buffer.toString();
  }
For this if the gaven string is:"an123*^%"
the result is: an123\*\^\%