Hi Perl monks I have a problem that I can't seem to get working and I was hoping you could help me please. I have a subrountine which I am using to parse a complex data structure and as I go through all the nested hashes I am looking for a list of certain keys and once I have all of these keys I am printing a line of output for each time I find a full set of keys. I am storing the list of keys in @keys_to_find and this looks like this: 

%volume
%mnt
%device
%perms
%user
%mntops
%other

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The subroutine I am using to parse the complex data structure and pass in @keys_to_find looks like this. This is able to correctly parse the data structure and print out individual lines containing all the values of each one of the keys in @keys_to_find. 

sub traverse_hash {
    my ($jsonhash, $found, @keys_to_find) = @_;
    my $results = 'results.txt';


    open(FILE, ">>$results");

    for my $key (sort keys %{$jsonhash}) {
        my $keyvalue = $jsonhash->{$key};
        
        if ('HASH' eq ref $keyvalue) {
            $found = {%$found, %{ traverse_hash($keyvalue, $found, @ke
+ys_to_find) }};
        }
        for my $find (@keys_to_find) {
            if ($key eq $find) {
                if ('HASH' eq ref $keyvalue) {
                    $found->{$key} = [ map $keyvalue->{$_}, sort keys 
+%$keyvalue ];
                } else {
                    $found->{$key} = $keyvalue;
                }
            } 
        }
    }    
    if (@keys_to_find == keys %$found) {
        my $count;
        $count = @{ (grep 'ARRAY' eq ref $_, values %$found)[0] // [] 
+};
        $count ||= 1;
        for my $i (0 .. $count - 1) {
            print FILE join(':', map { 'ARRAY' eq ref $_ ? $_->[$i] : 
+$_ } @{$found}{@keys_to_find}), "\n";
        }
        $found = {};
    }
    return $found;
    close(FILE);
}

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What I am struggling to work out how to do is to additionally pass into this subroutine an output format string so I can print the results in different formats rather than print lines containing every value for all the keys in @keys_to_find. So for example I want to pass in a a variable which contains an output format string like so: 

$output_format = '%mnt:%device:%volume:%perms';

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So with this $output_format string I want to be able to call the subroutine like this: 

traverse_hash(\%$decoded_json_obj, {}, @keys_to_find, $output_format);

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So when this subroutine is called like above I want it first to make sure that every key in @keys_to_find exists at each level in data structure (like it currently does) and then if all those keys exist then print out a line/s of output in the format of whatever keys are defined in $output_format string variable. The contents of $output_format will be different each time I call this subroutine so I can't pass into this subroutine a hardcoded string. I need to pass this in as a variable. Please can you help me with how to do this?

In reply to How to print a string in a specific format when parsing a complex data structure by newperluser2013

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