perl /home/lanx/perl/pm/int_pow.pl
=== comparing 2^50
--- 1.12589990684262e+15
is integer
-1: 	1125899906842623
1: 	1125899906842625
--- 1125899906842624
is integer
-1: 	1125899906842623
1: 	1125899906842625
=
=== comparing 2^63
--- 9.22337203685478e+18
is integer
-1: 	9.22337203685478e+18
1: 	9.22337203685478e+18
--- 9223372036854775808
is integer
-1: 	9223372036854775807
1: 	9223372036854775809
=