bernhard$ cat t.pl
use strict;
use warnings;
use Data::Dumper;

my %hash = (
-        KeyMinus => 'ValueMinus',
+       KeyPlus => 'ValuePlus',
);

print Dumper(\%hash);

bernhard$ perl t.pl 
$VAR1 = {
          'KeyPlus' => 'ValuePlus',
          '-KeyMinus' => 'ValueMinus'
        };