I'm not sure if a __DIE__ handler is the best way to go. I would use an eval block to trap the die. Something like this:

eval {
    $sqlquery = "SOME UPDATE STATEMENT";
    my $newsth = $dbh->prepare($sqlquery);
    $newsth->execute or die "3";
};

print $query->redirect(-location=>"$redirecturl?error=$@") if $@;
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When the die is called, the eval block will exit and $@ will be set to "3". If there is no error, then $@ will be set to the empty string.