use JSON::XS;
use 5.12.0;
use Data::Dump qw(dd);

my $j =
'{ "/": { "type": "dir", "files": [ { "p": { "type": "dir-link", "source": "/nfs/data/project", "files": [ { "xa": { "type": "dir", "files": [ { "tools": { "type": "dir", "files": [ { "sd": { "type": "dir", "files": [ { "su2av": { "type": "dir", "files": [ { "duf": { "type": "dir", "files": [ { "0.4.0": { "type": "dir-link", "source": "/nfs/vsa/project/xa/vuvua/su2av", "files": [ { "bin": { "type": "dir", "files": [ { "duf": { "type": "link-file", "source": ".run" } }, { ".run": { "type": "file" } } ] } } ] } } ] } } ] } } ] } } ] } } ] } } ] } }, { "nfs": { "type": "dir", "files": [ { "data": { "type": "dir", "files": [ { "project": { "type": "dir", "files": [] } } ] } }, { "vsa": { "type": "dir", "files": [ { "project": { "type": "dir", "files": [ { "xa": { "type": "dir", "files": [ { "vuvua": { "type": "dir", "files": [ { "su2av": { "type": "dir", "files": [] } } ] } } ] } } ] } } ] } } ] } } ] } }';

my $obj = decode_json($j);
dd $obj;

my %special_key = map { $_ => 1 } qw/type files source/;

find_paths($obj, []);

sub find_paths {
    my ($x, $paths) = @_;

    if (ref $x eq 'HASH') {
        while (my ($k, $v) = each %$x) {
            if(exists $special_key{$k}) {
                if($k eq 'files') {
                    find_paths($v, $paths);
                }
                elsif( $k eq 'type' && $v eq 'file' ) {
                    say join '/', @$paths;
                }
            }
            else {
                # a dir or file name
                # store it and continue
                find_paths($v, [@$paths, $k]);
            }
        }
    }
    elsif (ref($x) eq 'ARRAY') {
        if (scalar @$x > 0) {
            foreach my $node (@$x) {
                find_paths($node, $paths);
            }
        }
        else {
            say join '/', @$paths;
        }
    }
}