$ perl -w -Mstrict -de 1

Loading DB routines from perl5db.pl version 1.28
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(-e:1):   1
  DB<1> x { foo => () }
Odd number of elements in anonymous hash at (eval 5)[/usr/lib/perl5/5.8.8/perl5db.pl:628] line 2.
 at (eval 5)[/usr/lib/perl5/5.8.8/perl5db.pl:628] line 2
        eval '($@, $!, $^E, $,, $/, $\\, $^W) = @saved;package main; $^D = $^D | $DB::db_stop;
  { foo => () };

;' called at /usr/lib/perl5/5.8.8/perl5db.pl line 628
        DB::eval called at /usr/lib/perl5/5.8.8/perl5db.pl line 3412
        DB::DB called at -e line 1
0  HASH(0x65f420)
   'foo' => undef