Does this behave differently on Windows?

Seems so:

c:\test>perl
#!/usr/bin/perl -l

my $cmd = q(perl -e "chomp(my $ret = <STDIN>); exit $ret+1");

my $pid = open CMD, '|-', $cmd or die $!;

print CMD 98;

close CMD;
print "status from close:   ", $? >> 8;

waitpid $pid, 0;
print "status from waitpid: ", $? >> 8;
^Z
status from close:   99
status from waitpid: 99
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