From the Active State change log:

Bug Fixes and Changes since build 821

...

kill(0, $pid) was always returning TRUE in build 820 on Windows. It now returning the correct values again (bug 67519).

Upgrade. Works okay on AS 5.8.9:

c:\test>\perl32\bin\perl -le"print $]; print kill 0, $_ for 3844, 4844
+"
5.008009
1
0

[download]
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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In reply to Re^3: Simple way to find on Windows, whether a process is running by BrowserUk
in thread Simple way to find on Windows, whether a process is running by rovf

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