$constraint =~ m@
  ^\s*                              # skip all whitespace at beginning
  (                                 # start capturing
    /.+/                            # match a '/' any number of anychar '/'
    |                               # or
    m                               # char 'm' (start of a match)
    (.)                             # capture the delimiter
    .+                              # skip all the stuff 
    \2   	                       # upto the second occurance of the delimiter
  )                                 #end capture
  [cgimosx]*                        # match zero or more match options
  \s*$                              # skip white space
  @x