length(pack('J',0))

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in the past I used that, but then I realized that 64 bit IVs but 32 bit pointers and machine code Perls existed, so it is wrong. Another good way to telling is 
perl -MConfig -e "print $Config{ptrsize}"

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which will return 4 or 8, and is NOT the IV size

In reply to Re^2: How to tell 32 or 64 bit by bulk88
in thread How to tell 32 or 64 bit by esr

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