That's not trivial without knowing the previous version.

apart of using version control (like already mentioned)

For instant feedback

• run perl -c continuously in the background ( e.g. flycheck in emacs, default in Komodo)
• use automatic indentation while typing

For delayed analysis

• jump thru the last edits your editor recorded ( goto-last-change in emacs )
• indent the whole file, use perltidy if your editor doesn't support this ( indent-region in emacs) and do a visual check
• diff with the backup file your editor generated
• use tybalt89's suggestion to jump to the opening curly parsed by the editor for every closing one you find

update

perltidy has some additional features for code analysis, have a look.

IIRC there is also one to add extra info in a comment after each closing block.