If you need integers in the computer sense (IV/UV), 

length(pack('J', 0)) >= 8

[download]

or 

use Config qw( %Config );

$Config{uvsize} >= 8

[download]

uvsize refers to the size in bytes of such integers.

You need this if you use any of the following:

If you need integers in the mathematical sense, floats (NV) with at least 64 bits of precision would also do. 

use Config qw( %Config );

$Config{uvsize} >= 8 ||
   eval($Config{nv_overflows_integers_at}) >= 2**64

[download]

Every integer up and including eval($Config{nv_overflows_integers_at}) can be represented exactly as an NV.

Unless you've done something something, though, this is unlikely to get you more than 53-bits of precision.

In reply to Re: Best way to check for 64-bit support by ikegami
in thread Best way to check for 64-bit support by gflohr

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