split up query string and decode pairs into $val and $key
insert $key into params hash with value $val

##</code><code>##

foo.cgi?foo=mashed&foo=fried&foo=boiled&foo=tofu

##</code><code>##

if (defined $params{$key} && ref($params{$key}) eq "ARRAY") {

	# key has been seen at least twice now
	# the value is a an anonymous array, push the new value
	push (@{$params{$key}}, $val);
} 
elsif (defined($params{$key})) {

	# second time key has been seen
	# the value is a scalar, 'turn' it into an anonymous array
	$params{$key} = [$params{$key}, $val];
} 
else {
	# first time this key has been seen
	# assign the value as a scalar
	$params{$key} = $val; 
}