use YAPE::Regex::Explain;
die YAPE::Regex::Explain->new(qr/^(\w):\\(.+)\\?/)->explain;
__END__
The regular expression:

(?-imsx:^(\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):
----------------------------------------------------------------------
  ^                        the beginning of the string
----------------------------------------------------------------------
  (                        group and capture to \1:
----------------------------------------------------------------------
    \w                       word characters (a-z, A-Z, 0-9, _)
----------------------------------------------------------------------
  )                        end of \1
----------------------------------------------------------------------
  :                        ':'
----------------------------------------------------------------------
  \\                       '\'
----------------------------------------------------------------------
  (                        group and capture to \2:
----------------------------------------------------------------------
    .+                       any character except \n (1 or more times
                             (matching the most amount possible))
----------------------------------------------------------------------
  )                        end of \2
----------------------------------------------------------------------
  \\?                      '\' (optional (matching the most amount
                           possible))
----------------------------------------------------------------------
)                        end of grouping
----------------------------------------------------------------------