Re^2: Regular Expressions

[Roy Johnson]

There's an error in your understanding, if you think that the ^ should cause the expression not to match. It matches the beginning of the string, then multiple digits any number of times. Then the last capture has to match at the end of string.

You see, the * allows the group to match multiple times, and each time through, the capture group gets overwritten. So it can match everything up to "81" the first pass, then throw away that capture, capture "1" instead, and then the \1 matches, and the whole match succeeds.

Sounds like Java's regex engine just doesn't try hard enough.

[Anonymous Monk]

I understand that ^ here is "from the begining of the sting".
I didn`t know, that each match would overwrite capture group. Thanks. :)
I can`t find something about overwiting capture group in perlretut (am I a bad finder?). Are there any docs about it?
Thanks. :)

Nick <znick at inbox dot ru>

[Roy Johnson]

I don't think it's documented. It's just a case of having one place to store a capture and capturing into it multiple times. Each time a capture happens, the old value is overwritten. I wish it were documented, though.

[Anonymous Monk]

It is documented. perldoc perlre

    The numbered match variables ($1, $2, $3, etc.) and the related
    punctuation set ($+, $&, $`, $', and $^N) are all dynamically scoped
    until the end of the enclosing block or until the next successful match,
    whichever comes first. (See "Compound Statements" in perlsyn.)