If I want to use default value with Getopt::Long, I do:

    GetOptions (
        'item=s'  =>  \my $item = 'default',
    );
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If you want to work with a hash like you do, you can do:

    my %pars = (
       my $item = item => 'default value',
    );
    GetOptions (
       \%pars,
       "$item=s",
    );
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Abigail