While that looks nice, be very careful to not use a map that returns multiple entries per input with a long list before 5.6.1 is out. Unfortunately it currently scales quadratically:

%hash = map { $_, $_ } 1..20_000;
[download]

If that doesn't make you a believer, s/20/100/ and try again.

This applies to all versions of Perl with map until the upcoming 5.6.1.