DB<2> n
main::sub_find_last(dbg.pl:32):         return if !defined $X;
  DB<2> p $X
Use of uninitialized value $X in print at (eval 5)[/usr/lib/perl5/5.10/perl5db.pl:638] line 2.
 at (eval 5)[/usr/lib/perl5/5.10/perl5db.pl:638] line 2
        eval '($@, $!, $^E, $,, $/, $\\, $^W) = @saved;package main; $^D = $^D | $DB::db_stop;
print {$DB::OUT}  $X;

;' called at /usr/lib/perl5/5.10/perl5db.pl line 638
        DB::eval called at /usr/lib/perl5/5.10/perl5db.pl line 3436
        DB::DB called at dbg.pl line 32
        main::sub_find_last(undef) called at dbg.pl line 8

  DB<3>