in reply to Substitution bug on Unicode strings with Byte Order Mark (BOM)

A workaround is to start the pattern with (?!(?!)\x{100}) (where 0x100 is an arbitrary non-byte character). 
y $html = "\x{feff}<!DOCTYPE HTML PUBLIC> <div class=\"course_detail_b
+ox_content\"> </div>";
$html =~ s{(?!(?!)\x{100}).*?</div><div\s+class="course_detail_box_con
+tent">}{}s;

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(?!(?!)...) always matches exactly zero characters, and serves as a mechanism to include a non-byte character into the pattern.

In Section Seekers of Perl Wisdom