Method call walk-through
	l Consider a simple prepare call:   $dbh->prepare(...) l $dbh is reference to a DBI::db object (regardless of driver) l DBI::db::prepare is an alias for DBI dispatch method l Dispatch calls driver’s prepare method something like this:    my $inner_hash_ref = …     # from tie magic    my $implementor_class = …  # from DBI magic data    $inner_hash_ref->$implementor_class::prepare(...) l Driver code gets the inner hash so it has fast access to the hash contents
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