qwurx [shmem] ~ > perl -MO=Concise,-exec -e 'sub foo{"5"}; $c=4+foo;'
1  <0> enter 
2  <;> nextstate(main 2 -e:1) v
3  <$> const[IV 4] s
4  <0> pushmark s
5  <#> gv[*foo] s
6  <1> entersub[t3] sKS/TARG,1
7  <2> add[t4] sK/2
8  <#> gvsv[*c] s
9  <2> sassign vKS/2
a  <@> leave[1 ref] vKP/REFC
-e syntax OK