"a,a,c,i,a,c,..."
    
    # to be used in:
    my ($foo, $bar, $baz, ...) = unpack_line("a,a,c,i,a,c,...", $line);
    # or
    my $parser = My::Module->new( template => "a,a,c,i,a,c,..." );
    my ($foo, $bar, $baz, ...) = $parser->read_line();