Good point. To be clear that this is not just a "windows" issue, I got the same behavior (scalar string truncated at null byte when it was used as a file name in "open()") on macosx, which is basically unix, so I'd expect all unix and linux to behave the same way as well -- if it's "the OS's fault", this is one of those rare cases where all OS's can share the blame equally.

As for expecting better of Perl, I don't know what all happens under the covers during the conversion from SV to char*, but if it were to include doing the extra steps to check for string-internal null bytes, so it could throw some sort of exception or warning whenever it found one, I would expect most scripts to slow down noticeably.

Some folks might view that cost as too high for the resulting benefit, so it's relatively more worthwhile to force you to know about these implementation details (especially in your case, since you happen to know them already, anyway :D ).