Tip #9 from the Basic debugging checklist is to use YAPE::Regex::Explain to demystify Perl regular expressions:

The regular expression:

(?-imsx:(.*?)"_RVCT")

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
----------------------------------------------------------------------
  "_RVCT"                  '"_RVCT"'
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------
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