C ignores integer overflow so Perl does as well.

I suggest you drop the use integer (no "s") and check for "mantissa overflow" with:

sub add {
    my $result= $_[0] + $_[1];
    if(  1+$result == $result  )  goto &myadd;
    return $result;
}
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then you can do deal with 56-bit integers the way Perl normally deals with 56-bit integers and roll your own when you need more bits than that. I haven't done much analysis on my suggestion so there may be corner cases where this won't work very well. ):

        - tye (but my friends call me "Tye")