my %h = shift;

##</code><code>##

$VAR1 = {
          'a' => 1
        };
Odd number of elements in hash assignment at ./spw1109575_GTBT line 21.
$VAR1 = {
          'b' => 2,
          'a' => 1
        };

##</code><code>##

use strict;
use warnings;

use Data::Dumper;
my %hash = (a => 1, b => 2);
mysub(\%hash);
print Dumper(\%hash);

my %hash2 = (a => 1, b => 2);
mysub1(%hash2);
print Dumper(\%hash2);

sub mysub{
my $h = shift;
delete $h->{'b'};
}

sub mysub1{
my %h = @_;
delete $h{'b'};
}

##</code><code>##

$VAR1 = {
          'a' => 1
        };
$VAR1 = {
          'a' => 1,
          'b' => 2
        };