D:\>perl -MMath::BigInt -wle "$x = Math::BigInt->new(~0); $x++; while(\"$x\" == ~0){$x++}; print $x;"
18446744073709553665

##</code><code>##

D:\>perl -le "print 'ok' if 18446744073709553665 == 18446744073709554600;"
ok

##</code><code>##

D:\>perl -wle "print 'ok' if 18446744073709554600 == 18446744073709554599;"
ok