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

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

use Config qw( %Config );

$Config{uvsize} >= 8
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uvsize refers to the size in bytes of such integers.

You need this if you use any of the following:

• the numbers as operands to bitwise operators
• the numbers as operands to `..`/`...`
• pack 'Q'/unpack 'Q'
• hex literals larger than 0xFFFF_FFFF

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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
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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.