$ perl -MO=Concise,-exec -e'if (f()) { g() }'
1  <0> enter 
2  <;> nextstate(main 3 -e:1) v:{
3  <0> pushmark s
4  <$> gv(*f) s/EARLYCV
5  <1> entersub[t1] sKS/TARG,1
6  <|> and(other->7) vK/1
7      <0> pushmark s
8      <$> gv(*g) s/EARLYCV
9      <1> entersub[t2] vKS/TARG,1
a  <@> leave[1 ref] vKP/REFC
-e syntax OK

$ perl -MO=Concise,-exec -e'if (!f()) { g() }'
1  <0> enter 
2  <;> nextstate(main 3 -e:1) v:{
3  <0> pushmark s
4  <$> gv(*f) s/EARLYCV
5  <1> entersub[t1] sKS/TARG,1
6  <|> or(other->7) vK/1
7      <0> pushmark s
8      <$> gv(*g) s/EARLYCV
9      <1> entersub[t2] vKS/TARG,1
a  <@> leave[1 ref] vKP/REFC
-e syntax OK