Yes, [^\S \n] and \s(?<![ \n]) are equivalent. Well, should be.

Just tried it with my perl (v5.12.2), and [^\S \n] doesn't match \x{0085} and \x{00A0}

Sometimes it won't because of a bug, but that applies to both [^\S \n] and \s(?<![ \n]). See Re: Can I change \s?.

5.12 seems to have another problem on top of that.

5.12: 

$ perl -le'print "\x{00A0}" =~ /[^\S \n]/ ?1:0;'
0  # Expected

$ perl -E'say "\x{00A0}" =~ /[^\S \n]/ ?1:0;'
0  # Feature unicode_strings doesn't fix regexes yet.

$ perl -le'print "\N{U+00A0}" =~ /[^\S \n]/ ?1:0;'
0  # Surprised!

$ perl -le'print "\x{2660}\x{00A0}" =~ /[^\S \n]/ ?1:0;'
0  # Surprised!

[download]

(Last two are really the same.)

Now with what should be an equivalent pattern. 

$ perl -le'print "\x{00A0}" =~ /\s(?<![ \n])/ ?1:0;'
0  # Expected

$ perl -E'say "\x{00A0}" =~ /\s(?<![ \n])/ ?1:0;'
0  # Feature unicode_strings doesn't fix regexes yet.

$ perl -le'print "\N{U+00A0}" =~ /\s(?<![ \n])/ ?1:0;'
1  # \N always returns an upgraded string.

$ perl -le'print "\x{2660}\x{00A0}" =~ /\s(?<![ \n])/ ?1:0;'
1  # Forces the use of an upgraded string.

[download]

5.14: 

$ perl -le'print "\x{00A0}" =~ /[^\S \n]/ ?1:0;'
0  # Bug kept for backwards compatibility

$ perl -E'say "\x{00A0}" =~ /[^\S \n]/ ?1:0;'
1

$ perl -le'print "\N{U+00A0}" =~ /[^\S \n]/ ?1:0;'
1

$ perl -le'print "\x{2660}\x{00A0}" =~ /[^\S \n]/ ?1:0;'
1

[download]

In reply to Re^3: regexp: removing extra whitespace by ikegami
in thread regexp: removing extra whitespace by perlmax

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