How Perl Saved the Human Genome Project (1996)(bioperl.org)

    sub named_params {
      my %P = @_; # named params in hash %P
      my $foo = $P{bar} + $P{baz};
      return $foo * $P{multiplier};
    }
    
    my $rvalue = named_params( foo => 1, bar => 2, multiplier => 3 );

    sub named_params_hashref {
      my $P = shift;
      my $foo = $P->{bar} + $P->{baz};
      return $foo * $P->{multiplier};
    }
    my $rvalue = named_params_hashref({
      foo => 1,
      bar => 2,
      multiplier => 3,
    });