in reply to regex: Need help substituting

As toolic said, use an XML parser. But, in general terms, when I want to use a regex to change an unknown chunk of text that sits between two known chunks of text, I do it backwards from what you tried to do here. Instead of capturing the part I want to replace, I capture the parts I want to keep, and keep them. For instance: 

$string = 'blah blah blah <some_sort_of_tag>CHANGE ME</some_sort_of_ta
+g> blah blah blah';
$newtext = 'I AM NEW';
$string =~ s|^(.*<some_sort_of_tag>).+(</some_sort_of_tag>.*)$|$1$newt
+ext$2|;

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Aaron B.
My Woefully Neglected Blog, where I occasionally mention Perl.

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Re^2: regex: Need help substituting
by the_perl (Initiate) on Apr 08, 2012 at 07:36 UTC

    I have understood that using regex for this problem is not the preferred method, at all. It was however my intention to learn more about regexp, so for now, with your help I have come up with (using the backwards strategy) 

    # First match !
    $data =~ s|^(.*<section1>.*<rstate>).+(</rstate>.*</section1>.*)$|
+$1$newrstate$2|s;

# Second match!
    $data =~ s|^(.*<section2>.*<rstate>).+(</rstate>.*</subsection>.*<
+/subsection>.*</subsection>.*</section2>.*)$|$1$newrstate$2|s;

# Third match!
    $data =~ s|^(.*<section3>.*<rstate>).+(</rstate>.*</section3>.*)$|
+$1$newrstate$2|s;

    [download]

    Curious as I am, I will read up on the XML parser and try it as well to see how it compares. Thanks for the help!

[reply]
[d/l]

      I'm just curious as to why you're using the many if statements.
      I suppose the following should work: 

      $data=~ s{<rstate>[^<\n]+</rstate>}{<rstate>$new_text</rstate>}g

      [download]
      Note the use of the 'g' modifier.
      If you want to learn more about regular expressions in general, then Friedl's book is a must. It's one the most well-written books I've ever read on any subject and I highly recommend it.

[reply]
[d/l]

        Hi, I don't anylonger. I approached the problem the wrong way, and all I have now is the three lines above to substitute <rstate> at different specific places in the file. Totally agree on the book! I ordered it a while ago but haven't had the time to read it. I'm going to now since I will have good use for regexp in my present work. Thanks

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