The CPAN module YAPE::Regex::Explain is very helpful when trying to grok a regular expression pattern. Here's a command-line demonstration of it using your regex /(.*?)(\d+)/:

$ perl -MYAPE::Regex::Explain -e '
>     print YAPE::Regex::Explain->new(qr/(.*?)(\d+)/)->explain();
> '
The regular expression:

(?-imsx:(.*?)(\d+))

matches as follows:

NODE                     EXPLANATION
----------------------------------------------------------------------
(?-imsx:                 group, but do not capture (case-sensitive)
                         (with ^ and $ matching normally) (with . not
                         matching \n) (matching whitespace and #
                         normally):
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    .*?                      any character except \n (0 or more times
                             (matching the least amount possible))
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  (                        group and capture to \2:
----------------------------------------------------------------------
    \d+                      digits (0-9) (1 or more times (matching
                             the most amount possible))
----------------------------------------------------------------------
  )                        end of \2
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
$

[download]

Another regular expression tool I really like is RegexBuddy (http://www.regexbuddy.com/). It's well worth its modest price tag of USD 39.95.

In reply to Re: What is the output for this ?? by Jim
in thread What is the output for this ?? by sreenath

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