$ perl -MO=Concise -e'grep { f() } $x..$y;'
c  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 2 -e:1) v:{ ->3
8     <|> grepwhile(other->9)[t7] vK ->c
7        <@> grepstart K* ->8
3           <0> pushmark s ->4
-           <1> null lK/1 ->4
-              <1> null sK/1 ->8
-                 <@> scope sK ->8
-                    <0> ex-nextstate v ->9
b                    <1> entersub[t2] sKS/TARG,1 ->-
-                       <1> ex-list sK ->b
9                          <0> pushmark s ->a
-                          <1> ex-rv2cv sK ->-
a                             <#> gv[*f] s/EARLYCV ->b
-           <1> null lKM/1 ->7
6              <1> flop lKM ->7
e                 <1> flip[t6] lK ->7
4                    <|> range(other->5)[t5] lK/1 ->d
-                       <1> ex-rv2sv sK/1 ->e
d                          <#> gvsv[*x] s ->e
-                       <1> ex-rv2sv sK/1 ->6
5                          <#> gvsv[*y] s ->6
-e syntax OK