my @titles = ...; 
if (@titles == 1) {
   $BIGLIST{$title[0]} = [ @RESTOFFIELDS ];
}
elsif (@titles == 2) {
   $BIGLIST{$title[0]}{$titles[1]} = [ @RESTOFFIELDS ];
}
...etc.

##</code><code>##

my @titles = ...; 
my $ref = \%BIGLIST;
while (@titles > 1) {
   my $title = shift @titles;
   $ref = \($ref->{$title});
}
$ref->{$title[0]} =  [ @RESTOFFIELDS ];