code: public V put(String pKey, V pValue) {
          String key = (String) toUpper(pKey);
          return unwrap(entries.put(key, new BasicEntry<String, V>(key, pValue)));
      }
docs: Maps the specified key to the specified value in this map.
  Note: If the key used is a string, the key will not be case-sensitive.
  
  @param pKey   the map key.
  @param pValue the value.
  @return the previous value of the specified key in this map,
  or null if it did not have one.