What surprises me is that the bug doesn't seem to apply to both (with my perl), i.e. it only shows up with the negated char class

There's a bug that affects both -- the first test in 5.14 and the first two in 5.12 -- and there's a bug that doesn't.

You're quoting a comment about one when commenting on the other.

But what about the vertical tab U+000B?

It's in the Unicode property, but not \s. 

$ uniprops 0x0B
U+000B ‹U+000B› \N{LINE TABULATION}
    \v \R \pC \p{Cc}
    All Any ASCII Assigned Basic_Latin C Other Cc Cntrl Common Zyyy Co
+ntrol Pat_WS Pattern_White_Space PatWS POSIX_Cntrl POSIX_Space Space 
+VertSpace White_Space WSpace X_POSIX_Cntrl X_POSIX_Space

$ perl -E'say "\x0B" =~ /\p{Space}/ ?1:0;'
1

$ perl -E'say "\x0B" =~ /\s/ ?1:0;'
1

[download]

But I remember some characters not being in \s for historical reasons. 

$ diff -u0 <( unichars '\s' ) <( unichars '\p{Space}' )
--- /dev/fd/63  2011-11-04 21:18:53.160681893 -0400
+++ /dev/fd/62  2011-11-04 21:18:53.160681893 -0400
@@ -2,0 +3 @@
+ ---- U+000B LINE TABULATION

[download]

In reply to Re^5: regexp: removing extra whitespace by ikegami
in thread regexp: removing extra whitespace by perlmax

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