I've been using GPRename to batch-rename files; this is rather more efficient than individually correcting each file, but still seems to be less efficient than it might be, primarily because either I don't understand the regex syntax used, or because the regex implementation is incomplete1

Given a list of files of the following syntax:

(01) - title of file1.avi
(02) - title of file2.avi
(03) - title of file3.avi

I attempted to use the 'replace' (with the regex option selected, the case-sensitive option deselected):

(\(\d{2}\))

The preview then shows (given that I've specified no 'replace with' option as yet):

title of file1.avi
title of file2.avi
title of file3.avi

Which is great, clearly the regex is identifying the correct group (the (01)). Now, what I was hoping to do (using the JavaScript syntax) in the 'replace with' option is use:

$1

(I also tried using '$1', \1 and '\1')

This was just to check that I could access the matched group, and it seems I can't, the matched group is, as I suppose might be expected, replaced with the literal replacement string.

So, my question: is it possible to match a particular group of characters, in this case the numbers within the brackets, and then insert those into the replacement string? Therefore:

(01) title of file1.avi
(02) title of file2.avi
(03) title of file3.avi

Becomes:

01 title of file1.avi
02 title of file2.avi
03 title of file3.avi

1. I absolutely suspect the former, personally.