I'm not a windows user, but I do know from experience that there can be subtle differences in the configuration settings for various apps (e.g. attributes for command-line shell windows) that people tend to ignore or forget about when they compare two windows machines and call them "identical".

Maybe this is just a red herring, but if one machine out of several behaves different, it seems inaccurate to call it "identical" to the rest, and it might be worthwhile looking for the thing that makes it "not identical" (OS-patches/config/app-parameter-settings/etc...), rather than looking at just the perl code that triggers the deviant behavior.