The funny thing about "Chapter 5" of HBO's Perry Mason is that your reaction to the episode's final beats will depend wildly on your familiarity with the original Raymond Burr series or other notable adaptations. If you've never indulged and are just in the habit of watching whatever happens to be airing each week at 9 PM ET on HBO, your reaction to the ending will be "Wait, now he's a lawyer?" Meanwhile, pre-established fans of the property are yelling "About time!" As someone who has seen the original show but not for some time, …