See YAPE::Regex::Explain 
The regular expression:

(?-imsx:(\w+)\$=\$(\w+)\$=\$(\w+))

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:
----------------------------------------------------------------------
    \w+                      word characters (a-z, A-Z, 0-9, _) (1 or
                             more times (matching the most amount
                             possible))
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  \$                       '$'
----------------------------------------------------------------------
  =                        '='
----------------------------------------------------------------------
  \$                       '$'
----------------------------------------------------------------------
  (                        group and capture to \2:
----------------------------------------------------------------------
    \w+                      word characters (a-z, A-Z, 0-9, _) (1 or
                             more times (matching the most amount
                             possible))
----------------------------------------------------------------------
  )                        end of \2
----------------------------------------------------------------------
  \$                       '$'
----------------------------------------------------------------------
  =                        '='
----------------------------------------------------------------------
  \$                       '$'
----------------------------------------------------------------------
  (                        group and capture to \3:
----------------------------------------------------------------------
    \w+                      word characters (a-z, A-Z, 0-9, _) (1 or
                             more times (matching the most amount
                             possible))
----------------------------------------------------------------------
  )                        end of \3
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------

[download]
print+qq(\L@{[ref\&@]}@{['@'x7^'!#2/"!4']});

In reply to Re: regex; how it works by codeacrobat
in thread regex; how it works by sathiya.sw

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