$ perl -MO=Concise,foo,-exec -e'{ my $x; sub foo { $x } }'
main::foo:
1  <;> nextstate(main 2 -e:1) v
2  <0> padsv[$x:FAKE:]               <-- Is "FAKE": closed over
3  <1> leavesub[1 ref] K/REFC,1
-e syntax OK

##</code><code>##

$ perl -MO=Concise,-exec -e'{ my $x; { $x } }'
1  <0> enter
2  <;> nextstate(main 4 -e:1) v:{
3  <{> enterloop(next->b last->b redo->4) v
4  <;> nextstate(main 1 -e:1) v
5  <0> padsv[$x:1,3] vM/LVINTRO
6  <;> nextstate(main 3 -e:1) v
7  <{> enterloop(next->a last->a redo->8) v
8  <;> nextstate(main 2 -e:1) v
9  <0> padsv[$x:1,3] v               <-- Not "FAKE": in scope
a  <2> leaveloop vK/2
b  <2> leaveloop vK/2
c  <@> leave[1 ref] vKP/REFC
-e syntax OK