== code == 

use warnings;
use strict;
 
use Fcntl;
 
my $flag = O_RDONLY;
 
my $amode = do {
               if     ($flag & O_RDONLY) { "r" }       # XXX: isn't this 0?
               elsif  ($flag & O_WRONLY) { ($flag & O_APPEND) ? "a" : "w" }
               elsif  ($flag & O_RDWR)   {
                   if ($flag & O_CREAT)  { "w+" }
                   else                  { ($flag & O_APPEND) ? "a+" : "r+" }
               }
           };

print "$amode\n"; # Prints "0" for O_RDONLY