Something you can do to make your code easier to read (beyond the formating in this forum) is to use q() and qq(). For example, where you do this:

$INSERT_SQL="INSERT INTO trg_table(".
"column1,".              
"column2".                  
") VALUES ".
"(?,".
"?)";
[download]

Try this instead:

$INSERT_SQL= q{
INSERT INTO trg_table( column1, column2 )
 VALUES (?,?)
};
[download]

Because you do not need variable interpolation here, you can use single quotes. If you need to do variable interpolation, use qq() instead.