After assimilating what little info I could glean off the web, my conclusion it that Cygwin is the issue. The cygwin.dll provides Unix emulation for all system calls, including such things as malloc(). These, in turn, interact with the Windows environment.

ActivePerl doesn't have to go through a middle-man, and can interact with Windows directly.

However, will all the other features I get with Cygwin, I'm not inclined to trade it in for straight Windows/DOS. If I'm ever in need of extreme speed for Perl on a Windows box, then I might consider a parallel installation of ActivePerl for just that task.