I probably would not do this as a one-liner. The trimming can easily be handled with map, though.

my ($catno, $desc, $pack, $min, $gst,
    $cost, $unitcost, $retail, $barcode) =
   map { s/\s+$//; $_ }
   unpack("A7 x2 A30 A4 A4 x13 A7 x15 A8 A8 A8 x13 A13", $_);
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The call to map makes a new list from the old list after removing any trailing whitespace.

It seems like there's a way to get unpack to return an empty field. But that escapes me at the moment.

Update: as jwkrahn points out, my change shouldn't be needed because of the 'A'. I should have looked at the unpack template instead of the OP reference to needing to strip the whitespace.