One of our packages generates itself from a table of named exceptions and its own source code
https://livesql.oracle.com/apex/livesql/file/content_CCDPAOR8IXKYVUT9YHMCZ7W3U.html
This way it is easy to have a central place to define named exceptions.

And each object has in its header comment the version number in a form like CM#102. So if you want to check the object versions you can simply ask the database

SELECT  s1.name  "Name"
       ,s1.type  "Typ"
       ,SUBSTR(REGEXP_SUBSTR(s1.text,'CM#[[:digit:]]*'),4)  "Version"
FROM    user_source s1
WHERE   s1.line = ( SELECT  MAX(s2.line)
                    FROM    user_source s2
                    WHERE   INSTR(s2.text,'CM#') > 0
                    AND     s2.name = s1.name
                    AND     s2.type = s1.type
                    )
ORDER BY s1.name
        ,s1.type

Name           Typ          Version
-----------------------------------
ScanFolder     JAVA SOURCE  1
SEPIS$SENDMAIL PACKAGE      6
SEPIS$SENDMAIL PACKAGE BODY 9
...

Or if you want to search in your code for occurrences of <searchstring>
Or if you lost the source code of a procedure you can simply spool it into a file
Or ...