hello, i want to know how do i select a line in a listbox by the right click of the mouse. ...

What system? (Tk? Wx? ...)

(For list boxes in HTML forms, you'll need something that runs in the browser such as JavaScript. Perl won't be of use except on the few machines that have PerlScript installed.)

Update: The root post was changed. The original question made no mention of Tk. I've added a quote from the original version.