in reply to Look Ahead:

because it must be /([0-9]+)(?=welcome)welcometo india/ to match

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Re^2: Look Ahead:
by nvivek (Vicar) on Apr 02, 2010 at 09:14 UTC
    I knew how to match the string but I want to know why it is working like that?Explain me?
[reply]
      Because sometimes you need to look ahead without actual matching.

      For example: 
      $num = scalar reverse "1000000000000";
$num =~ s/(\d\d\d(?=\d))/\1,/g;
print scalar reverse $num;

      [download]
      will print 1,000,000,000,000
[reply]
[d/l]

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