I, too, got lost and gave up pretty quickly (although I think JavaFan has set the OPer on the right path), but  @- and  @+ are regex-related special variables, so things like  $-[0] and  $+[0] are valid.

Another oddity of the OPer's original code is

my @LINES=<DATA>;
my $tLINES=@LINES;
foreach $RECORD (@LINES[0..$tLINES-1]) {
    ...
    }
[download]

This seems to boil down to (assuming you don't just use a  while loop)

my @LINES = <PROPERFILEHANDLE>;
foreach $RECORD (@LINES) {
    ...
    }
[download]