! defined and $_ = ' ' for @$row;

I was wondering if some monks could explain the above statement to me. A few things are confusing.

1) I know ! means "no", so does the first part mean 'not defined'?

2) I've never understood what this means '$_', and if I'm not mistaken you can also use the underscore with arrays & hashes like '@_' and '%_'?

3) How can you set an array and a variable at the same time? In other words, what does @$row mean or what is it accomplishing?

Thanks monks! OOOOMMMM!!

In reply to Simple Noob Question by jdlev

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