$ perl584 -MO=Concise -e'print "a", $b+1;'
9  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 1 -e:1) v ->3
8     <@> print vK ->9
3        <0> pushmark s ->4
4        <$> const(PV "a") s ->5
7        <2> add[t1] sK/2 ->8
-           <1> ex-rv2sv sK/1 ->6
5              <$> gvsv(*b) s ->6
6           <$> const(IV 1) s ->7

$ perl584 -MO=Concise,-exec -e'print "a", $b+1;'
1  <0> enter 
2  <;> nextstate(main 1 -e:1) v
3  <0> pushmark s
4  <$> const(PV "a") s
5  <$> gvsv(*b) s
6  <$> const(IV 1) s
7  <2> add[t1] sK/2
8  <@> print vK
9  <@> leave[1 ref] vKP/REFC