3. Without the "_cached", it does not seems to change anything.....

I used DBI->trace as Arguile wisely suggested, and it looks like all is fine... strange...
The Statement is prepared, the parameter binded, and the all thing is executed successfully.
BUT it returns nothing ([0] items).

if I cut and paste the SQL from the Perl, and replace the :mob and :acc by the binded values in the log file, it returns the value fine (the entrie does exist in the table...).

Maybe I look for an error in the Perl when I should go and seek the wisdom of the DBA Administrator as he might have error log of my activities....