You need to test whether the ref value of $data->{foo} is an arrayref: if so, it's a list of messages; otherwise it's a single message. And that's pretty easy: 
    if (ref $data->{foo} eq "ARRAY") {
        # list
    }
    else {
        # single message
    }

[download]
What I sometimes like to do in such situations--where I can have either an arrayref or a single value--is coerce the single value into an array ref. Then I can use the same code to deal with both situations: 
    unless (ref $data->{foo} eq "ARRAY") {
        $data->{foo} = [ $data->{foo} ];
    }

[download]

In reply to Re: Testing Complex Data Structures by btrott
in thread Testing Complex Data Structures by epoptai

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