my %hash = (a => 10, b => 20, c => 30);
my $hashRef = \%hash;

$hashRef->{d} = 40;
&PrintHashref($hashRef);

$hashRef->{e} = 50;
&PrintHashref($hashRef);
# -------------------------------------
sub PrintHashref {
  my ($hashref) = @_;

  foreach (keys %$hashRef) {
    print "$_ => $hashRef->{$_}\t";
  }
  print "\n";
}