`hello prints variants of hello, world. To control format, pass a single letter as command-line argument. "@"=>"hello, world", "H"=>"hello, world.", P=>"hello, world!", "X"=>"hello, world,", take 1 letter later to s/h/H/, 2 letter later to s/d,/d/, 4 letter later to s/w/W/, lowercase to remove newline.