At least part of your problem seems to be with while (defined(<>)). The <> takes a line from the filehandle, and then you test it for being defined, and (continue to) loop if it is. Unfortunatly, unlike using while(<>) it doesn't actually assign the value into $_. To do that you can use while (defined($_=<>)), but that's exactly equivilent to while(<>).

I would advise that you look at using split, instead of regex for this task. It looks like it probably would be better suited for this data.