committable6

query

6c sub infix:<j>{$^l.comb.tail eq $^r.comb.head??(|$l,$r)!!|@};say [Xj] <te tt>,<fg et>,<wd td>; # usually you'll do this

result

¦«2015.12,2016.02,2016.03,2016.04,2016.05,2016.06,2016.07.1,2016.08.1,2016.09»: ((te et td))
¦«2016.10,HEAD»: Use of Nil in string context
  in sub infix:<j> at /tmp/tNdcOdwv9t line 1
Use of Nil in string context
  in sub infix:<j> at /tmp/tNdcOdwv9t line 1
Use of Nil in string context
  in sub infix:<j> at /tmp/tNdcOdwv9t line 1
Use of Nil in string context
  in sub infix:<j> at /tmp/tNdcOdwv9t line 1
Use of Nil in string context
  in sub infix:<j> at /tmp/tNdcOdwv9t line 1
Use of Nil in string context
  in sub infix:<j> at /tmp/tNdcOdwv9t line 1
((te et td))