You can only accept and deliver signals which your OS supports. To get a list of them, use e.g.
perl -le "print for sort keys %SIG"
update: the OP was modified after my answer, which doesn't make any sense know. Originally the OP was asking about how to implement or use or deliver (I don't remember very well) the USR1 signal on Windows.
Output from the above snippet on my box (linux)
ALRM
BUS
CHLD
CLD
CONT
FPE
HUP
... more signals...
UNUSED
URG
USR1
USR2
VTALRM
WINCH
XCPU
XFSZ
which is a list of the signals for that OS. I bet perl on windows features a different set of keys in %SIG. |