# All of the packages are Foo::<something>
my $BASE_PACKAGE = "Foo";

$type_string = /^TYPE:\s*(.+)$/;

# Type is used as the package name
my $type = $1;
my $sub = LoadPlugin($type, "process_line");
&{$sub}($arg1, $arg2, ...);

sub LoadPlugin
{
  my $package = shift();
  my $routine = shift();

  # construct Foo::$type
  my $plugin = $BASE_PACKAGE . "::" . $package;

  # try to load it
  eval "require $plugin";
  if($@)
  {
     die "Couldn't load $plugin";
  }
  
  # if we've loaded successfully return a
  # ref to the function
  my $sub = \&{$plugin . '::' . $routine};

  return $sub;
}