borisz meant the first group of four digits, which is perfect if you can count on the data format.

Why not do your loop all in one line?

my @years = map /(\d{4})/, @dates;
[download]

Of course, you could use any regex that satisfies in the code above. Note that the parenthesis are critical, without them you'll wind up with a list full of '1'.

Update Thanks to Roy Johnson I fixed my regex. Left out the \ for the \d.