请问如何在此代码中将位置参数更改为命名参数？

Question

如果有人能告诉我如何在此Perl代码中将位置参数更改为命名参数，我将不胜感激。

#!/usr/bin/perl -w

sub diskUsageMon {
    my ($hash_ref, $array_ref) = @_;

    unless ( open(DF, "df -kh 2>&1 |") ) {
        chomp $!;
        push $array_ref, "Failed to start command df", "Reason: $!";
        return 1;
    }; # Unless

    while ( <DF> ) {
        next if /^Filesystem/;
        @df = split;
        my ($mount, $use) = @df[5,4];
        $hash_ref->{$mount} = $use;
    }; # While

    close DF;

    return 0;
}; # sub

#---------------------------------------------------------#

%hash_ref = ();
@array_ref = ();

if ( &diskUsageMon(\%hash_ref, \@array_ref) ) {
    die "Error detected!\n", "Reason: ", join("\n", @array_ref), "\n";
};