Windows' fork emulation is just an emulation, and it shows a bug there. With a genuine fork you sould see:

inner
outer
inner
outer
[download]

or a possible but unlikely reversal of the middle two. Fork produces two processes where there was one, each continuing from the location of fork. Both processes see and do both print statements. Here's a version which skips "outer" for the child.

BEGIN {
    my $cpid = fork;
    print "inner\n";
    exit 0 unless $cpid;
}
print "outer\n";
[download]

It would be more to the point to ask if Windoew' emulation can be fixed to match the real thing.

Update: Oh, that's what you were asking. </sigh>