Lines 1-4 establish 10 variables. If you do the math, each variable is a digit equal to one less than the number of underscores in its name. The function _$ takes three numbers and returns the character you get by combining the characters. So _$ 1,0,3 returns ASCII character 103. So lines 5-9 print out a message one character at a time. Looking up the codes, you get "Hello World!" Fun puzzle!