$ perl -MO=Concise,-src tst_b_xref3.pl|grep var
tst_b_xref3.pl syntax OK
# 1: unless ($var1) {
3                 <#> gvsv[*var1] s ->4
# 2:     $var2++;
8                    <#> gvsv[*var2] s ->9
# 5:     $var3++;
e                    <#> gvsv[*var3] s ->f