It seems to me your script should work, since you are reading it line-by-line. My guess is your Perl or OS dosn't have "large-file-support".

But is it possible that no one thus far has noticed the

foreach $line (<FH>) {
[download]

line in the OP's code?!? Well, maybe the problem will still be there, but there's a reason why we recommend against doing so all the time. To the OP: just try using a while loop instead. Until you have a fully functional Perl 6 installation available, that is!

Update: naikonta noticed.