$ perl -MO=Concise -e 'X: next X'
4  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(X: main 1 -e:1) v:{ ->3
3     <"> next("X") v ->4
-e syntax OK
$ perl -MO=Concise -e 'X: goto X'
4  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(X: main 1 -e:1) v:{ ->3
3     <"> goto("X") v ->4
-e syntax OK