>perl -MO=Concise -e"print( 4 + 1 * 2 )"
6  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 1 -e:1) v ->3
5     <@> print vK ->6
3        <0> pushmark s ->4
4        <$> const[IV 6] s ->5           <--- 4+1*2
-e syntax OK

>perl -MO=Concise -e"print( 4 + $x * 2 )"
a  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 1 -e:1) v ->3
9     <@> print vK ->a
3        <0> pushmark s ->4
8        <2> add[t3] sK/2 ->9          \
4           <$> const[IV 4] s ->5      |
7           <2> multiply[t2] sK/2 ->8  | <--- 4+$x*2
-              <1> ex-rv2sv sK/1 ->6   |
5                 <#> gvsv[*x] s ->6   |
6              <$> const[IV 2] s ->7   /