while (@data = <DATA>) {
    ...
}

##</code><code>##

for($i=0;$i<$#data;$i++){

##</code><code>##

for my $line (@data) {

##</code><code>##

my @tokens;
while (<DATA>) {
    if (/\.\.(AU|BD):/) {
        if ($1 eq 'AU') {
            print join( ',',@tokens),"\n", @tokens = () if @tokens;
        }
        chomp (my $line = <DATA>);
        push @tokens, $line;        
    }
}
print join( ',',@tokens),"\n", @tokens = () if @tokens;