You could always use something like what I just threw together below. But like you said, the code becomes repetitive. Here it is: provides both parameter checking and default values.

sub do_something {
  my %default = (             # declare all valid parameter
    foo => 'foo argument',    # names, providing a default
    bar => 'bar argument',    # value at the same time (set
    baz => undef              # to undef for no default)
  );

  my %params = (%default, @_);

  for (keys %params) {
    warn "unknown parameter '$_' passed to do_something()"
      unless exists $default{$_};
  }

  # now do stuff.
}
[download]