Why NSTask doesn't work as Terminal.app ?

Regular arguments work just fine but when I have an argument with a parameter, I get errors…
The argument list to be pass to NSTask is really a token list: each item on the command line separated by a space is an argument for NSTask where for the original command a group of tokens makes an argument according to the syntax of the tool.
In other words, an argument like
-l option is to be expanded in two tokens/arguments by NSTask: @"-l" and @"option".