Re: What this pattern matches

With a little YAPE::Regex::Explain magic:

$ perl -MYAPE::Regex::Explain -e 'print YAPE::Regex::Explain->new(qr/^
+(.+)_[^_]+$/)->explain' 

The regular expression:

(?-imsx:^(.+)_[^_]+$)

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):
----------------------------------------------------------------------
  ^                        the beginning of the string
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    .+                       any character except \n (1 or more times
                             (matching the most amount possible))
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  _                        '_'
----------------------------------------------------------------------
  [^_]+                    any character except: '_' (1 or more times
                           (matching the most amount possible))
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
[download]

or a little more tersely. Match any string that contains at least one character before and one character after the last underscore that appears in the string.

-enlil

Comment on Re: What this pattern matches Download Code

Replies are listed 'Best First'.
Re^2: What this pattern matches by zerogeek (Monk) on May 12, 2006 at 08:22 UTC
First, let me say that this is one of the best explanations of a regex that I have seen. Now, can anyone give a good example of 1 or 2 lines that would match and 1 or 2 that would NOT match? Allow me to reword and provide a possible match example: Match a line with at least one underscore (if more than one, the following applies ONLY to the LAST underscore) that is both preceeded AND followed by at least one character. Match: I_love Match: I_love_perl Match: I_love_perl_! No Match: I_love_perl!_ Am I right?	[reply]
Re^2: What this pattern matches by mikeock (Hermit) on May 12, 2006 at 15:37 UTC
What a neat module. I was un-aware of this until seeing this post!	[reply]