sub score {
  $_=pop;                                                       #  7

  s#(.)/(?=(.).|.?$)#$1.($1?10-$1:'x').lc$2#ge;                 # 45

  s/X(?=(..).)/X$1/g;                                           # 19

  y/Xx/9/+eval join'+',/./g                                     # 25
}
#                                                                ___
#                                                                 96