You probably had a primary/unique key set on the filename. If you want to overwrite it, just add a delete SQL before you do the insert. If you want custom error messages, you need to turn off automatic error handling with something like this -

my $dbh = DBI->connect( blah, blah,
     {PrintError => 0,
      RaiseError => 0} ) or die "message";

...

$sth->execute() or die "print your own error message here."
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