use warnings;
use integer; # makes no difference

# 144115188075868217 == (2 ** 57) + 12345
$string1 = '144115188075868217';
$string2 = '144115188075868217crap'; 

$string1 += 0;

{
no warnings 'numeric';
$string2 += 0;
}

print $string1, "\n";
#prints 144115188075868217 ... correct

print $string2, "\n";
# prints 144115188075868224 ... wrong