sleep is interuptable if safe signals are disabled.

It's suppose to be, but it isn't on Windows. The following won't to print 'OK' like it the documentation says it does. With or without safe signals.

>perl -wle"$SIG{INT}=sub{}; sleep; print 'OK'"
[download]

The implementation of safe signals makes sleep's uninterruptibility a bigger issue than it was before, but the bug already existed.

OP who must be using windows otherwise he wouldn't have encountered the problem.

Every problem he's had occurs on non-Windows as well. And he said he's using Red Hat Enterprise Linux.