map {chomp $_->[2]; $data{$_->[0]}{$_->[1]}{$_->[2]} = ''} [split /\s+
+/]
    for <DATA>;
[download]

Could be written more simply as:

map {$data{$_->[0]}{$_->[1]}{$_->[2]} = ''} [split]
    for <DATA>;
[download]

Or without using map in a void context:

$data{$_->[0]}{$_->[1]}{$_->[2]} = '' for map [split], <DATA>;
[download]

:-)