I notice that Net/CIDR/Lookup.pm has "use integer"

According to Shift Operators:

Note that both << and >> in Perl are implemented directly using << and >> in C. If use integer (see Integer Arithmetic) is in force then signed C integers are used."
This means that right shifts will be sign extended. Anything with the msb set will be sign extended and remain negative. 

$ perl -E 'use integer; say 0x80000000 >> 31'
-1

[download]

RichardK's suggestion above would avoid this issue.

In reply to Re: Bit fiddling madness by sn1987a
in thread Bit fiddling madness by mbethke

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