Utf8 correct regex for CamelCase (WikiWord) in perl

Question

Here was a question about the CamelCase regex. With the combination of tchrist post i'm wondering what is the correct utf-8 CamelCase.

Starting with (brian d foy's) regex:

/
    \b          # start at word boundary
    [A-Z]       # start with upper
    [a-zA-Z]*   # followed by any alpha

    (?:  # non-capturing grouping for alternation precedence
       [a-z][a-zA-Z]*[A-Z]   # next bit is lower, any zero or more, ending with upper
          |                     # or 
       [A-Z][a-zA-Z]*[a-z]   # next bit is upper, any zero or more, ending with lower
    )

    [a-zA-Z]*   # anything that's left
    \b          # end at word 
/x

and modifying to:

/
    \b          # start at word boundary
    \p{Uppercase_Letter}     # start with upper
    \p{Alphabetic}*          # followed by any alpha

    (?:  # non-capturing grouping for alternation precedence
       \p{Lowercase_Letter}[a-zA-Z]*\p{Uppercase_Letter}   ### next bit is lower, any zero or more, ending with upper
          |                  # or 
       \p{Uppercase_Letter}[a-zA-Z]*\p{Lowercase_Letter}   ### next bit is upper, any zero or more, ending with lower
    )

    \p{Alphabetic}*          # anything that's left
    \b          # end at word 
/x

Have a problem with lines marked '###'.

In addition, how to modify the regex when assuming than numbers and the underscore are equivalent to lowercase letters, so W2X3 is an valid CamelCase word.

Updated: (ysth comment)

for the next,

• any: mean "uppercase or lowercase or number or underscore"

The regex should match CamelWord, CaW

• start with uppercase letter
• optional any
• lowercase letter or number or underscore
• optional any
• upper case letter
• optional any

Please, do not mark as duplicate, because it is not. The original question (and answers too) thought only ascii.

Answer 1

I really can’t tell what you’re trying to do, but this should be closer to what your original intent seems to have been. I still can’t tell what you mean to do with it, though.

m{
    \b
    \p{Upper}      #  start with uppercase code point (NOT LETTER)

    \w*            #  optional ident chars 

    # note that upper and lower are not related to letters
    (?:  \p{Lower} \w* \p{Upper}
      |  \p{Upper} \w* \p{Lower}
    )

    \w*

    \b
}x

Never use [a-z]. And in fact, don’t use \p{Lowercase_Letter} or \p{Ll}, since those are not the same as the more desirable and more correct \p{Lowercase} and \p{Lower}.

And remember that \w is really just an alias for

[\p{Alphabetic}\p{Mark}\p{Decimal_Number}\p{Letter_Number}\p{Connector_Punctuation}]