use strict;
use warnings;
use Test::More tests => 3;
use bignum;

sub xe{
 $_[0]*log($_[0])+log(atan2(1,1)*8*$_[0])/2
  + 1/(12*$_[0]) - 1/(360*($_[0]**3)) + 1/(1260*($_[0]**5));
}

my ($m, $n, $r) = ( 2**96, 3*(10**6), 1*(10**6) );

my $e=exp(xe($m-$n)+xe($m-$r)-xe($m)-xe($m-$n-$r));

is( $e      , 1,    '$e should equal 1'     );
is( 1-$e    , 0,    '1-$e should equal 0'   );
is( 1-"$e"  , 0,    '1-"$e" should equal 0' );

##</code><code>##

1..3
ok 1 - $e should equal 1
not ok 2 - 1-$e should equal 0
#     Failed test (bigtest.pl at line 17)
#          got: '1'
#     expected: '0'
ok 3 - 1-"$e" should equal 0
# Looks like you failed 1 test of 3.