I can't replicate your issue, but searching Google turns up something very similar. What version are you using? I get good behavior on v5.10.1 built for MSWin32-x86-multi-thread and v5.10.1 (*) built for x86_64-linux-gnu-thread-multi.

Update:On v5.8.9 built for MSWin32-x86-multi-thread I can get the warning you are citing. Specifically, perl -e "print hex('24d0e803adb7')" outputs

Integer overflow in hexadecimal number at -e line 1.
40479664352695
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This can actually be suppressed with a no warnings declaration, though I'd make sure that the math is still being respected:

{
    no warnings;
    $hex="24d0e803adb7"; 
    $dec=hex($hex);
}
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