$ perl -MO=Concise,ret,empty,label -e'sub ret {return}; sub empty {()}; sub label {LABLE:};' 
main::ret:
4  <1> leavesub[1 ref] K/REFC,1 ->(end)
-     <@> lineseq KP ->4
1        <;> nextstate(main 2 -e:1) v ->2
3        <@> return K ->4
2           <0> pushmark s ->3
main::empty:
7  <1> leavesub[1 ref] K/REFC,1 ->(end)
-     <@> lineseq KP ->7
5        <;> nextstate(main 4 -e:1) v ->6
6        <0> stub P ->7
main::label:
9  <1> leavesub[1 ref] K/REFC,1 ->(end)
8     <;> nextstate(LABLE: main 6 -e:1) P ->9
-e syntax OK