What Perl and OS are you using? With ActivePerl 5.6.1, 5.8.0 and 5.8.8 all print the following in WinXP. 

Null char detected in >filename1.txt <
Null char detected in >filename2 .txt<

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I even confirmed the "space" is a NUL.

In reply to Re^2: How to specify a Null char in a match operation by ikegami
in thread How to specify a Null char in a match operation by Nik

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