Using "[]" as brackets in a regular expression

Am trying to re-organize my music folder and would like to header each letter (eg. [A] Artists, [B] Artists, etc). I have been able to use $validate($replace(F:\F PreInbox$left('[%albumartist%,1]')\%albumartist%\%album% $num(%year%,4), , ), %mediatype%,'_') which gives me the structure I want minus the "[]" .. I have been playing around with the positioning of the '[ and the ]' but have yet to get it correct....any assistance would be appreciated.

Ok my error, this isn't in a regular expression however the question still remains. Would also like to try to figure out if I can set up after processing via some if not all of BPM processing, KeyFinder and Album Art Downloader where I can move the folder(s) that I just processed (if in already in the order I wanted) directly to my Media/Music Folder bypassing the Pre Inbox folder?

The square brackets serve as some kind of "if" statement: if there is nothing in the named field variable don't ouput the text in brackets - a text option.
If you want to get the brackets as literals, you have to use '[' and ']' like '['%year%']'.

Thank you for the response from looking at your example, I was missing the extra ' . I only had '[%year]' ....

Ok so I am still having positioning issues even though I have followed the above

$validate($replace(F:\F PreInbox$left('['%albumartist%,1']')\%albumartist%\%album% $num(%year%,4), , ), %mediatype%,'_')

Is not working the way that I am trying to get it to do....just where should these brackets be placed for my desired results as I have moved them around and still have not been able to get it to work properly..the assistance is greatly appreciated.

What about:

You can test your expression with the function Convert>Teg-Tag.


would always return the [ as this is the first character from the left.