If you don't want to change your SQL then you will have to create a problem at the database end by ensuring some of your SQL fails - e.g., manually create a row which will cause a constraint to fail in your SQL, delete a key, change permissions etc. The possibilities are endless so I'm not listing all I can think of here.

I am sorry again i am disturbing YOU. i don't want to change either in sql query or deleting rows. I am asking that, is there any mechanism in perl that a person can throw error intentionally. Because i am using

 $SIG{__WARN__} = \&WARN_Handler;
$SIG{__DIE__} = \&DIE_Handler;
[download]

And i also written code for handle error using WARN_HANDLER AND DIE_HANDLER

warn and die???