lanx@lanx-1005HA:~$ cat /tmp/tst_bxref.pl
use strict;
use warnings;


my $a=1;


print($a);
sub bla {
}



{
    my $a=2;
    print($a);
    bla($a);
    
}

print($a);




lanx@lanx-1005HA:~$ perl -MO=Xref,-d /tmp/tst_bxref.pl 
File /tmp/tst_bxref.pl
  Subroutine (main)
    Package (lexical)
      $a                i5, i15, 8, 16, 17, 21
    Package main
      &bla              &17
/tmp/tst_bxref.pl syntax OK



lanx@lanx-1005HA:~$ perl -MO=Xref,-d,-r /tmp/tst_bxref.pl 
/tmp/tst_bxref.pl (main)           5 (lexical)       $ a                intro
/tmp/tst_bxref.pl (main)           8 (lexical)       $ a                used
/tmp/tst_bxref.pl (main)          15 (lexical)       $ a                intro
/tmp/tst_bxref.pl (main)          16 (lexical)       $ a                used
/tmp/tst_bxref.pl (main)          17 (lexical)       $ a                used
/tmp/tst_bxref.pl (main)          17 main            & bla              subused
/tmp/tst_bxref.pl (main)          21 (lexical)       $ a                used
/tmp/tst_bxref.pl syntax OK