My String Tools Package

CREATE OR REPLACE PACKAGE PkgStringTools IS
  FUNCTION CharacterAt(str1 VARCHAR2, pos INTEGER) RETURN VARCHAR2;
  FUNCTION Substring(str1 VARCHAR, pos1 INTEGER, pos2 INTEGER) RETURN VARCHAR2;
  FUNCTION Swap(str1 VARCHAR2, pos1 INTEGER, pos2 INTEGER) RETURN VARCHAR2;
  FUNCTION Shuffle(str1 VARCHAR2) RETURN VARCHAR2;
END PkgStringTools;
/
CREATE OR REPLACE PACKAGE BODY PkgStringTools IS
  FUNCTION CharacterAt(str1 VARCHAR2, pos INTEGER) RETURN VARCHAR2 IS
  BEGIN
    IF pos < 1 OR pos > LENGTH(str1) THEN
      raise_application_error(-20000, 'Subscript out of range: ' || pos);
    END IF;
    RETURN SUBSTR(str1, pos, 1);
  END;

  FUNCTION Substring(str1 VARCHAR, pos1 INTEGER, pos2 INTEGER) RETURN VARCHAR2 IS
  BEGIN
    RETURN SUBSTR(str1, pos1, pos2 - pos1 + 1);
  END;

  FUNCTION Swap(str1 VARCHAR2, pos1 INTEGER, pos2 INTEGER) RETURN VARCHAR2 IS
    FIRST INTEGER := pos1;
    SECOND INTEGER := pos2;
    temp INTEGER;
  BEGIN
    IF FIRST = SECOND THEN
      RETURN str1;
    END IF;
    IF FIRST > SECOND THEN
      temp := SECOND;
      FIRST := SECOND;
      SECOND := temp;
    END IF;
    IF SECOND = LENGTH(str1) THEN
      RETURN Substring(str1, 1, FIRST - 1) || CharacterAt(str1, SECOND) || Substring(str1, FIRST + 1, SECOND - 1) || CharacterAt(str1, FIRST);
    ELSE
      RETURN Substring(str1, 1, FIRST - 1) || CharacterAt(str1, SECOND) || Substring(str1, FIRST + 1, SECOND - 1) || CharacterAt(str1, FIRST) || Substring(str1, SECOND + 1, LENGTH(str1));
    END IF;
  END;

  FUNCTION Shuffle(str1 VARCHAR2) RETURN VARCHAR2 IS
    shuffled VARCHAR2(32767) := str1;
    VALUE NUMBER;
  BEGIN
    FOR i IN 1..LENGTH(shuffled)-1 LOOP
      VALUE := ROUND(DBMS_RANDOM.VALUE(i, LENGTH(shuffled)-1));
      shuffled := Swap(shuffled, i, VALUE);
    END LOOP;
    RETURN shuffled;
  END;
END PkgStringTools;
/