sub foo1 {
  my ($c, $d, $e, $f) = @_;
  return $d * f;
}

sub foo2 {
  my ($c, $d, $e, $f) = @_;
  return $c + $d + $e + $f;
}

sub do_foo {
  my $which = $_[0] ? \&foo1, \&foo2;
  $which->(1, 2, 3, 4);
}