DBI->connect_cached( $dsn, $username, $auth, {
    PrintError => 1,
    RaiseError => 1,
    AutoInactiveDestroy => 1})or die "Could not connect to: " $DBI::errstr ."\n";

##</code><code>##

my $checkExist = $dbh->prepare("INSERT IGNORE INTO your statement here");

if (!$checkExist->execute()) {
    die "Error: ". $checkExist->errstr ."\n";
}

##</code><code>##

use Try::Tiny;

try {
    ...
	$sth->execute();
    ...
} catch {
    # $sth->err and $DBI::err will be true if error was from DBI
    warn $_; # print the error (which Try::Tiny puts into $_)
    ... # do whatever you need to deal with the error
};