I see where the problem is, it's in the Checkbutton -variable option. If you comment out the -variable option it works.

$f->Checkbutton( -text=>$qqq,
        -offvalue=>'', 
        -onvalue=>$qqq,
    #    -variable=>\$qqq, 
        -command=>\&hostls,
)->pack(-side=>'left');
[download]

Checkbuttons can be tricky. They have a -variable and a -textvariable option. My guess is that with the -variable option you are converting $qqq to a number. $www is unaffected because you don't have it in the Checkbutton. I can't say for sure exactly how to handle it, because I get confused myself when I play with those Checkbuttons too deeply. If you read the perldoc for Tk::CheckButton, the variable option is used to specify a reference to a variable to set to indicate whether or not this button is selected. It is probably undef,1, or 0. Anyways that is where the problem lies.