sub dostuff {
  my %arg = @_;

  # Access named parameters like $arg{foo}
}

dostuff( foo => 'FOO', bar => 1 );

##</code><code>##

sub_with_callbacks (
  red    => sub { my %arg = @_; .. $arg{foo} .. },
  green  => sub { my %arg = @_; .. $arg{foo} .. },
  blue   => sub { my %arg = @_; .. $arg{foo} .. },
  yellow => sub { my %arg = @_; .. $arg{foo} .. }
);

##</code><code>##

sub_with_callbacks (
  red    => sub { .. $_{foo} .. },
  green  => sub { .. $_{foo} .. },
  blue   => sub { .. $_{foo} .. },
  yellow => sub { .. $_{foo} .. }
);