Your code cannot run at all:

    $maketable = ("CREATE TABLE $newuser (A,B,C,D,E)");
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This is not valid SQL (except maybe in SQLite). But that doesn't matter because you never run that statement.

    $sth = execute();
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This should never work. You need to call the ->execute() method on your statement handle. Unless you also have defined (but not shown to us) a subroutine with the name execute.