POSIX sigaction might give you access to the pid, BUT the docs say it's not often implemented

sigaction

    Detailed signal management. This uses POSIX::SigAction objects for
+ the action and oldaction arguments (the oldaction can also be just a
+ hash reference). Consult your system's sigaction manpage for details
+, see also POSIX::SigRt.

...


The following are also defined by POSIX/SUSv3, but unfortunately not v
+ery widely implemented:

    pid         the process id generating the signal
    uid         the uid of the process id generating the signal
    status      exit value or signal for SIGCHLD
    band        band event for SIGPOLL
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