open STDERR,">","stderr.log" or die $!;
open STDOUT,">","stdout.log" or die $!;
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It's a bit more clear and obvious. Redirecting STDIN *to* a file makes no sense, but I suppose you could do:

open STDIN,"<","stdin.txt" or die $!;
print while <>;
[download]

But I'm not sure what the purpose of that would be.