diff --git a/doc/src/sgml/plpgsql.sgml b/doc/src/sgml/plpgsql.sgml
index 7d23ed4..9d9e362 100644
*** a/doc/src/sgml/plpgsql.sgml
--- b/doc/src/sgml/plpgsql.sgml
*************** $$ LANGUAGE plpgsql STRICT IMMUTABLE;
*** 5650,5668 ****
  <programlisting>
  --
  -- instr functions that mimic Oracle's counterpart
! -- Syntax: instr(string1, string2, [n], [m]) where [] denotes optional parameters.
  --
! -- Searches string1 beginning at the nth character for the mth occurrence
! -- of string2.  If n is negative, search backwards.  If m is not passed,
! -- assume 1 (search starts at first character).
  --
  
  CREATE FUNCTION instr(varchar, varchar) RETURNS integer AS $$
- DECLARE
-     pos integer;
  BEGIN
!     pos:= instr($1, $2, 1);
!     RETURN pos;
  END;
  $$ LANGUAGE plpgsql STRICT IMMUTABLE;
  
--- 5650,5668 ----
  <programlisting>
  --
  -- instr functions that mimic Oracle's counterpart
! -- Syntax: instr(string1, string2 [, n [, m]]) where [] denotes optional parameters.
  --
! -- Search string1, beginning at the nth character, for the mth occurrence
! -- of string2.  If n is negative, search backwards, starting at the abs(n)'th
! -- character from the end of string1.
! -- If n is not passed, assume 1 (search starts at first character).
! -- If m is not passed, assume 1 (find first occurrence).
! -- Returns starting index of string2 in string1, or 0 if string2 is not found.
  --
  
  CREATE FUNCTION instr(varchar, varchar) RETURNS integer AS $$
  BEGIN
!     RETURN instr($1, $2, 1);
  END;
  $$ LANGUAGE plpgsql STRICT IMMUTABLE;
  
*************** BEGIN
*** 5688,5700 ****
      ELSIF beg_index &lt; 0 THEN
          ss_length := char_length(string_to_search);
          length := char_length(string);
!         beg := length + beg_index - ss_length + 2;
  
          WHILE beg &gt; 0 LOOP
              temp_str := substring(string FROM beg FOR ss_length);
!             pos := position(string_to_search IN temp_str);
! 
!             IF pos &gt; 0 THEN
                  RETURN beg;
              END IF;
  
--- 5688,5698 ----
      ELSIF beg_index &lt; 0 THEN
          ss_length := char_length(string_to_search);
          length := char_length(string);
!         beg := length + 1 + beg_index;
  
          WHILE beg &gt; 0 LOOP
              temp_str := substring(string FROM beg FOR ss_length);
!             IF string_to_search = temp_str THEN
                  RETURN beg;
              END IF;
  
*************** DECLARE
*** 5721,5759 ****
      length integer;
      ss_length integer;
  BEGIN
!     IF beg_index &gt; 0 THEN
!         beg := beg_index;
!         temp_str := substring(string FROM beg_index);
  
          FOR i IN 1..occur_index LOOP
              pos := position(string_to_search IN temp_str);
! 
!             IF i = 1 THEN
!                 beg := beg + pos - 1;
!             ELSE
!                 beg := beg + pos;
              END IF;
! 
!             temp_str := substring(string FROM beg + 1);
          END LOOP;
  
!         IF pos = 0 THEN
!             RETURN 0;
!         ELSE
!             RETURN beg;
!         END IF;
      ELSIF beg_index &lt; 0 THEN
          ss_length := char_length(string_to_search);
          length := char_length(string);
!         beg := length + beg_index - ss_length + 2;
  
          WHILE beg &gt; 0 LOOP
              temp_str := substring(string FROM beg FOR ss_length);
!             pos := position(string_to_search IN temp_str);
! 
!             IF pos &gt; 0 THEN
                  occur_number := occur_number + 1;
- 
                  IF occur_number = occur_index THEN
                      RETURN beg;
                  END IF;
--- 5719,5750 ----
      length integer;
      ss_length integer;
  BEGIN
!     IF occur_index &lt;= 0 THEN
!         RAISE 'argument ''%'' is out of range', occur_index
!           USING ERRCODE = '22003';
!     END IF;
  
+     IF beg_index &gt; 0 THEN
+         beg := beg_index - 1;
          FOR i IN 1..occur_index LOOP
+             temp_str := substring(string FROM beg + 1);
              pos := position(string_to_search IN temp_str);
!             IF pos = 0 THEN
!                 RETURN 0;
              END IF;
!             beg := beg + pos;
          END LOOP;
  
!         RETURN beg;
      ELSIF beg_index &lt; 0 THEN
          ss_length := char_length(string_to_search);
          length := char_length(string);
!         beg := length + 1 + beg_index;
  
          WHILE beg &gt; 0 LOOP
              temp_str := substring(string FROM beg FOR ss_length);
!             IF string_to_search = temp_str THEN
                  occur_number := occur_number + 1;
                  IF occur_number = occur_index THEN
                      RETURN beg;
                  END IF;