http://www.perlmonks.org?node_id=1067597


in reply to Re: Perl RE; how to capture, and replace based on a block?
in thread Perl RE; how to capture, and replace based on a block?

Thank you educated_foo.

" Keep adding "VAR," between the parens in #2 as long as Perl complains about 'Global symbol "VAR"...' Someone should probably write an Acme:: module to do this automatically."

I'll be glad to. Just as soon as I figure this all out. :)

My biggest hangup, I think, is that I'm quite comfortable with sed. But sed is "greedy" by default, and while Perl RE can be. It's not, by default, and that's what I need here (not greedy).

s/\<\/div\>/,/\<\/body\>/

[download]
will match my pattern in sed. But it will match from the first </div> till the first </body>. Which is too much.

Thanks again for the response, educated_foo

--Chris

Yes. What say about me, is true.

Replies are listed 'Best First'.
Re^3: Perl RE; how to capture, and replace based on a block?
by Laurent_R (Canon) on Dec 18, 2013 at 07:46 UTC
    By default, Perl RE are greedy. Have you considered the possibility that the end of line might be more than \n (if the file is coming from Windows, for example)?
[reply]
      Greetings, Laurent_R, and thanks for the reply.

      Oh yes. I'm keen on the \n v \r v \n\r thing, and you're absolutely correct. Except, in my case, I'm on a *NIX box, and I've written the files myself. So I know they're utf-8 (no BOM), with newlines, no "hard" returns. :)

      Maybe it's just the examples I was reading (perlrequick, perlretut, and perlfaq6) but I got the impression that Perl RE wasn't greedy. More Perl RE reading, I guess.

      Thanks again, for the response Laurent_R.

      --Chris

      Yes. What say about me, is true.
[reply]

        Hi Chris

        just a quick example on greedy and non greedy quantifiers, under the Perl debugger: 

          DB<1> $string = "foo bar foo bar foo";

  DB<2> x $string =~ /(fo.*ar)/
0  'foo bar foo bar'
  DB<3> x $string =~ /(fo.*?ar)/
0  'foo bar'
  DB<4>

        [download]
        As you can see the default "*" quantifier is greedy, so that the regex tries to match as much as possible. Using the modified "*?" quantifier, the regex becomes non greedy. You will see the same type of result if you try the "+" and the "+?" quantifiers.

[reply]
[d/l]
Re^3: Perl RE; how to capture, and replace based on a block?
by Anonymous Monk on Dec 18, 2013 at 07:29 UTC

    ... sed ...

    here is my test program 

    use re 'debug';
$_ = q{</div>
</body>};
print 'does it match ', int m{\<\/div\>\n\<\/body\>};

    [download]
[reply]
[d/l]

In Section Seekers of Perl Wisdom