Yes I've seen a few $dbh->do(); statements in the Deitel book. Is that wrong or dangerous?

do() isn't at all dangerous, but it is reserved for SQL statements that don't return data.

  $dbh->do("DELETE FROM foo WHERE bar = 47");
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is O.K., but

  $dbh->do("SELECT bar FROM foo");
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isn't. This is spelled out in the on-line DBI documentation.