$ perl -MO=Concise,-exec -e'@b = sort { foo() } @a'
1  <0> enter
2  <;> nextstate(main 2 -e:1) v
3  <0> pushmark s
4  <0> pushmark s
5  <#> gv[*a] s
6  <1> rv2av[t6] lK/1
7  <@> sort lKS*        --> I guess the * means the sub is
8  <0> pushmark s           attached to the op rather than
9  <#> gv[*b] s             found on the stack.
a  <1> rv2av[t2] lKRM*/1
b  <2> aassign[t7] vKS
c  <@> leave[1 ref] vKP/REFC
-e syntax OK