*VARSIZE parameter overwrites other variables.

Dear all,
   
  I have a procedure accepting an *VARSIZE parameter.
  On return other variables ar overwritten and as result, crashing the program.
  The Procedure is defined as follow:
  D P_AMTCHR        PR             1a                      
D   AMTNUM                      14  0                    
D   AMTCHR                      19A   OPTIONS(*VARSIZE)  
D   AMTLNG                      10i 0 VALUE              
D   AMTSGN                       1A   CONST              
D   AMTCCY                       3A   OPTIONS(*NOPASS)
   
  The execution is as follow:
  C                   EVAL      P_OK=P_AMTCHR(BITCHRSTP:
C                             SFLD6:%LEN(SFLD6):'-')  
C                   EVAL      P_OK=P_AMTCHR(BITCHRIBN:
C                             SFLD7:%LEN(SFLD7):'-')  
   
  Variable SFLD7 is in this example 12 positions (but could be any).
  The value in SFLD7 on return is correct.
  Variables defined after SFLD7 are altered.
   
  Here the specific part of the dump:
  SFLD7                 CHAR(12)             '       4.00-'             
                      VALUE IN HEX         '40404040404040F44BF0F060'X
SFLMAX                PACKED(2,0)          04.              '4040'X   
SSTAT                 CHAR(11)             '   ered    '
   
  Or better said, the procedures just returns 19 positions overwritting 7 
positions in other variables.
  I can understand what is happening (although I do not want to understand it).
  Is this intended to happen?
   
  Regards,
  Eduard Sluis.