sniff sniff, do i smell homework?

your first problem is that you don't test to see if the regex matches, because you want to treat lines differently (> lines become hash keys, lines after then become their data). the next two lines make no sense, you append every $_ to $str but never clear it. at the end of the loop it will contain a concatenated copy of every line of data post-chomp.

i'm not going to post working code because this is very basic logic; i'm guessing you were given an assignment to do this and got frustrated. throw an if (/regex/) { this is a key } else { this is a data line } and you'll start going somewhere