Well Nuances code below :

for (1, 9, 3, 60, 10, 20, 40, 35, 35, 35, 35, 35, 10,
         3, 20, 20, 20, 50, 1, 1, 1, 1, 6, 6) {
    $cu_fmt .= "\%-${_}.${_}s,"
}

print "format = $cu_fmt \n";
[download]

led me to this:

@fmt = (1, 9, 3, 60, 10, 20, 40, 35, 35, 35, 35, 35, 10,
         3, 20, 20, 20, 50, 1, 1, 1, 1, 6, 6);

$cu_fmt = join ',', (map { "\%-${_}.${_}s" } @fmt );

print "format = $cu_fmt \n";
[download]

but Im not sure either version is particularly easy to follow :-), cheers for the input though people.