To get Perl to use more that one write(2) when outputting "aaa\n" you'd have to set $| to a true value and use more than one Perl statement to output those 4 characters.

Though, there is a very distinct chance that this is exactly what is happening. Hard to say for sure. So, I tried commenting out the

$| = 1;
[download]

line. Didn't work though.