It is useful to remember that qx//is backticks. It's just another syntax to get there. It doesn't exercise any different code path, it won't behave any different, except how the parser finds the end of the string (you could type qx/foo `blah`/ without needing special escape characters to get the backquotes into the shell).
Also, q//is single-quoted, and qq//is double-quoted. Same thing.