That question came up before. You're getting the warning because you turned on warnings on someone else's code (by using -w instead of use warnings;). The warning is harmless. It can be fixed by changing

if($^O eq "MSWin32") {
    eval '*F_GETFL = sub {0};';
    eval '*F_SETFL = sub {0};';
    eval '*O_NONBLOCK = sub {0}; ';
}
[download]

to

if($^O eq "MSWin32") {
    eval '*F_GETFL = sub () {0};';
    eval '*F_SETFL = sub () {0};';
    eval '*O_NONBLOCK = sub () {0}; ';
}
[download]

I can't comment on any crashing.