It may not be the most efficient way, but when I have a question regarding when a particular feature was added, I scan my way through the perldelta PODs. There are a handful of them, and so its usually easier to write a little one-liner that scans through them looking for some keyword, except in the case of things like "our", where the word is so common in the English language that its difficult to craft a RE to find the specific usage relating to the addition of the our function.

To this end, I find grep quite useful, as it returns the entire line. I usually script for output that tells the POD name, the line number, and the content of the line that matched. I may get a few 'hits', but its easy to filter out the chafe at that point.

The perldeltas are named perldelta (for the Perl version currently installed on your system), and also such names as perl561delta, perl580delta, and so on, for each previous version.