>perl -MO=Concise,f -e"sub f { $x }"
main::f:
3  <1> leavesub[1 ref] K/REFC,1 ->(end)
-     <@> lineseq KP ->3
1        <;> nextstate(main 1 -e:1) v ->2
-        <1> ex-rv2sv sK/1 ->-
2           <#> gvsv[*x] s ->3
-e syntax OK