Select Code to Download

                # We're hunting the (properly bracketed)
$str =~         # 'm \d+' occurrences.  They must be 
...
     (?:m \s \d+ \s)*   # Any number of m \d+ groups.
     bar)/xg;   # Finally terminated with bar (though not
                #  necessarily the end of string.)

  - starts at the current 'beginning' of the string
  - matches the 'm \d+' at the current position
...
  - matches (aft) all the remaining 'm \d+' and the final bar 
     -  and THROWS AWAY the fore and aft matches  (they're non-capturi
+ng)