I often get an error saying something about conflict with an existing I/O operation.

Where are you seeing that message? When, (ie. after which operation in your code) is it displayed? What is the exact text of the message?

Print the error messages (using $! and/or $^E (I find the latter most useful under win32), as a part of your die messages:

... or die "...: $! [$^E]";
[download]

Then you'll be able to tell us what the error actual message is, and we stand a chance of helping you. The likely problem is that you don't have the appropriate permissions, or you've supplied a bad machine name (Do you really have a machine named "A"?), but the exact text of the message would identify the cause.