[jQuery] Trouble constructing selector string.

[rinse_my_phonebook]

                        var t = 'input.ffControl[value="Add a Value"]:first';
                        var s = 'input.ffControl[value="Add a 
'+$(this).attr('class')
+'"]:first';
                        if(s == t) { alert(s); }
                        $(t,this).val('gotcha');

Hi there, Can anyone help me understand why changing the fourth line
of the above snippet to

                        $(s, this).val('gotcha')

does not have the effect that the orignal line has when the alert on
line 3 always shows?

Many thanks in advance for any effort, I appreciate it,

Rinse