I really, really like this approach, and think it should be implemented in Perl 6, or if possible even sooner. This is a much cleaner solution than the clumsy variable evaluation.

Here's my try to match simple xml-like data: 

%
    ^
    \s*
    (                               # <1>
        <
        \s*
        ([a-zA-Z:]+)                # <2/>
        (?:
            \s*[a-zA-Z:]*
            \s* = \s*
            (?:'[^']*'|"[^"]*")
        )*
        \s*
        (/\s*)?                     # <3/>
        >

        (?:[^<>]* | (?1))*          # Update: added * to (?:)

        (?(3)|
            <\s*/\s*\2\s*>
        )
    )                               # </1>
    \s*
    $
%x

[download]
This is not at all xml-compliant, but at least handles simple data. 
<foo><bar></bar></foo> # Match
<foo><bar></foo></bar> # No match
<foo><bar/></foo>      # No match (WRONG)
<foo><bar></foo>       # No match
<foo bar=baz/>         # No match
<foo bar="baz">        # No match
<foo bar="baz"/>       # Match
<    fooo   /  >       # Match
<foo/>foo              # No match
foo<foo/>              # No match
<foo>foo</foo>         # Match
<foo><bar/>foo</foo>   # No match (WRONG)
<a><b><c></c></b></a>  # No match (WRONG!!)

[download]
Could it be that backreferences (like \2) in this case or conditionals (like (?(3)) don't work the way they should, when your patch is used?.

UPDATE The new version of robin's patch does parse the deeper recursion correctly. See also: Re: Recursive Regex: Update. 

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geW91IHNlZSBpdD8gIC0tIEp1ZXJk

In reply to Re: More Power to your Regex by Juerd
in thread More Power to your Regex by robin

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