Perl doesn't do things to be 'cool'. It does things to be useful. Besides, what 'cool' thing did you expect perl to do with that, anyway?

You embedded a literal newline in your regular expression. That matches newlines in the string you match against as you can see by your test code. Putting a backslash in front of it does nothing since it's not a special character.

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print map { my ($m)=1<<hex($_)&11?' ':'';
$m.=substr('AHJPacehklnorstu',hex($_),1) }
split //,'2fde0abe76c36c914586c';
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