sub abc {
  my %param = @_;
  for my $required qw( banana nut ) {
    die "missing: $required" unless defined $param{$required};
  }
  # etc
}

##</code><code>##

sub abc {
  # set up defaults
  my %param = (
      apples => 'green',
      banana => 'yellow',
    );
  # now override with any passed params
  %param = @_;
  for my $required qw( banana nut ) {
    die "missing: $required" unless defined $param{$required};
  }
  # etc
}

##</code><code>##

  my %passed = @_;
  (@param{ keys %passed }) = values %passed;