the outermost transaction will issue a L</txn_commit>, and txn_do() can be
called in void, scalar and list context and it will behave as expected.
-Unlike L</DBIx::Class::Storage/dbh_do>, the coderef will I<not> be
-automatically retried on error.
+Please note that all of the code in your coderef, including non-DBIx::Class
+code, is part of a transaction. This transaction may fail out halfway, or
+it may get partially double-executed (in the case that our DB connection
+failed halfway through the transaction, in which case we reconnect and
+restart the txn). Therefore it is best that any side-effects in your coderef
+are idempotent (that is, can be re-executed multiple times and get the
+same result), and that you check up on your side-effects in the case of
+transaction failure.
=cut