..."three-pipe problem" is mentioned in "The Red-Headed League", the Canon, to my knowledge, never said "two-pipe problem" - though I know a few films that do.
"Everyone will bare witness to the fact that I am acting in self-defense...
No, sir, a gentleman! Only a ruffian deals a blow with the back of the hand,
a gentleman uses the straight left - and I, sir, am a gentleman."