Hmmm... Seems to be in fact a Windows x POSIX.pm issue. I tried to create a PoC using exactly the same code you had on t/serving.t on Windows to reproduce the problem: 
C:\>perl -e "use POSIX qw(:sys_wait_h SIGHUP SIGKILL);
my $child_pid; if(!($child_pid = fork())) { exit(0); } 
kill(SIGKILL, $child_pid);"

Your vendor has not defined POSIX macro SIGHUP, used at -e line 1

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Although only the "use" does not signal the problem, when you put it on kill(), it hangs. Same thing for SIGKILL...

I'm using Windows XP and POSIX.pm version 1.09, just in case this is POSIX issue. 
C:\> perl -v

This is perl, v5.8.8 built for MSWin32-x86-multi-thread
(with 50 registered patches, see perl -V for more detail)

Binary build 820 [274739] provided by ActiveState

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In reply to Re^4: Hoping for some beady eyes on my first CPAN submission by garu
in thread Hoping for some beady eyes on my first CPAN submission by aufflick

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