%parms value when calling from SQL UDF.

I'm recieving unexpected values when using %parms on a procedure called via
an SQL UDF.

Here's my procedure (located on a *SRVPGM), it basically wraps the call to
PadR(), becouse the latter one is coded to handle strings of length not
supported by SQL (65535a):

p PadRSQL         B                   export
d PadRSQL         PI          5000a   varying
d   str                       5000a   const varying
d   len                          5p 0 const
d   pchr                         1a   const varying options(*nopass)

d cp              s              5i 0
d RtnStr          s                   like(PadRSQL)

c                   eval      cp = %parms
c                   if        cp = 2
c                   eval      RtnStr = PadR(str: len)
c                   else
c                   eval      RtnStr = PadR(str: len: pchr)
c                   endif
c                   return    RtnStr

p PadRSQL         E

I've created two copies of the UDF with the same name having two and three
parameters:

CREATE FUNCTION
  PADRSQL2 (pSTR  VARCHAR(5000),
            pLEN  DEC(5),
            pCHAR VARCHAR(1))
  RETURNS VARCHAR(5000)
  LANGUAGE RPGLE
  EXTERNAL NAME 'BABIB/PADR(PADRSQL2)'
  SPECIFIC PADRSQL2A
  DETERMINISTIC
  NO EXTERNAL ACTION
  PARAMETER STYLE GENERAL;

CREATE FUNCTION
  PADRSQL2 (pSTR  VARCHAR(5000),
            pLEN  DEC(5))
  RETURNS VARCHAR(5000)
  LANGUAGE RPGLE
  EXTERNAL NAME 'BABIB/PADR(PADRSQL2)'
  SPECIFIC PADRSQL2B
  DETERMINISTIC
  NO EXTERNAL ACTION
  PARAMETER STYLE GENERAL;

Always i call the function i get -1 returned by %parms, which leads to an
inappropiate behavior.
Is %parms not allowed when calling from an SQL UDF ? i've never read
anything like this....

Thanks in advance...

Carlos Kozuszko.