if the user is perlwise (and only then), my favourite option is to simply put the config-data as perl code in the config-file, like

"root"          => "/path/to/root",
"filepath"      => "/path/to/files",
"ftp_instances" =>
[
    {
        "sourcepath" => "/source/path/on/server",
        "savepath"   => "/save/files/here",
    },
    {
        "sourcepath" => "/source/path/on/server",
        "savepath"   => "/save/files/here",
    },
]
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Then you can simply read the file, do

eval "%CFG = (" . readfile("cfg") . ");";
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and you´re gone.

The benefit is that you can safely bring in all kind of difficult data (newlines etc.), and you can use an idiom you are pretty much used to.

just my $ 2/100