Actually what the system function is doing is not 'quoting' the parameters but directly supplying them to the OS exec call.

Note that argument processing varies depending on the number of arguments. If there is more than one argument in LIST, or if LIST is an array with more than one value, starts the program given by the first element of the list with arguments given by the rest of the list. If there is only one scalar argument, (...)

While qx supplies the command to the shell for parsing for arguments. And this happens in the 'only one scalar argument' case above too (which I cut out for brevity).

You might try to look at IPC::Open2 or IPC::Open3 functions. They can be called in simmilar fashions as system.