... any other method ... storing the found or empty value into variables ?

Did you take a look at the code here? (Update: Also here.) And if you need a quick-and-dirty replacement for  $RE{num}{real} from Regexp::Common if you have difficulty installing it, try
    my $rx_amount = qr{ (?> [-+]? (?: \d+ (?: [.] \d*)? | [.] \d+)) }xms;
It's semi-tested and should be enough to move forward with.