.../POE/Kernel.pm
BEGIN {
   ...
    if ($^O eq 'MSWin32') {
        *{ __PACKAGE__ . '::RUNNING_IN_HELL' } = sub { 1 };
    } else {
        *{ __PACKAGE__ . '::RUNNING_IN_HELL' } = sub { 0 };
    }
   ...
}

.../POE/Resource/FileHandles.pm:
### Some portability things.

# Provide dummy constants so things at least compile.  These constants
# aren't used if we're RUNNING_IN_HELL, but Perl needs to see them.

BEGIN {
  if (RUNNING_IN_HELL) {
    eval '*F_GETFL = sub { 0 };';
    eval '*F_SETFL = sub { 0 };';
  }
}