Personally, I think mixing signals and threads is a very bad idea, so I don't. But, maybe the following output from running your program on windows will give you some clues to your mistakes:

c:\test>junk73
I'm the parent pid-> 4440
No such signal: SIGSIGUSR1 at C:\test\junk73.pl line 26.
No such signal: SIGSIGUSR1 at C:\test\junk73.pl line 26.
In the thread threads=SCALAR(0x35a9020) tid->1
1
In the thread threads=SCALAR(0x362daa8) tid->2
2
3
4
5
Unrecognized signal name: USR1 at C:\test\junk73.pl line 14.
Perl exited with active threads:
        1 running and unjoined
        0 finished and unjoined
        1 running and detached
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He he :)

c:\test>perl -wE"$SIG{SIGSPUTNIK} = 'ignore'"
No such signal: SIGSIGSPUTNIK at -e line 1.
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