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    use Getopt::Long;
    GetOptions(
       'single=s' => \(my $single = ''),
        'multi=s' => \(my @multi  = ()),
    );

    use Getopt::Long;
    GetOptions(
       'single=s' => \(my $single = ''),
        'multi=s' => do { use vars '@multi'; \@multi },
    );