$ perl -MO=Concise,-src tst_b_xref4.pl|perl -pe 'substr $_, -1, 0, " "x(68-length$_) . "  #:$1" if /(^#|nextstate|var\d+)/;'
tst_b_xref4.pl syntax OK
j  <@> leave[1 ref] vKP/REFC ->(end)
1     <0> enter ->2
# 1: for (                                                           #:#
2     <;> nextstate(main 3 tst_b_xref4.pl:1) v:{ ->3                 #:nextstate
4     <1> preinc[t2] vK/1 ->5
-        <1> ex-rv2sv sKRM/1 ->4
3           <#> gvsv[*var1] s ->4                                    #:var1
5     <0> unstack v* ->6
i     <2> leaveloop vK/2 ->j
6        <{> enterloop(next->c last->i redo->7) v ->f
-        <1> null vK/1 ->i
h           <|> and(other->7) vK/1 ->i
g              <1> postinc[t4] sK/1 ->h
-                 <1> ex-rv2sv sKRM/1 ->g
f                    <#> gvsv[*var2] s ->g                           #:var2
-              <@> lineseq vK ->-
b                 <@> leave vKP ->c
7                    <0> enter v ->8
# 6:     $var4++;                                                    #:#
8                    <;> nextstate(main 1 tst_b_xref4.pl:6) v:{ ->9  #:nextstate
a                    <1> preinc[t8] vK/1 ->b
-                       <1> ex-rv2sv sKRM/1 ->a
9                          <#> gvsv[*var4] s ->a                     #:var4
d                 <1> preinc[t6] vK/1 ->e
-                    <1> ex-rv2sv sKRM/1 ->d
c                       <#> gvsv[*var3] s ->d                        #:var3
e                 <0> unstack v ->f