Try this: http://www.nntp.perl.org/group/perl.beginners/2007/09/msg95440.html
See Example 1 from Class::Struct docs:
Example 1
Giving a struct element a class type that is also a struct is how structs are nested. Here, Timeval represents a time (seconds and microseconds), and Rusage has two elements, each of which is of type Timeval .
use Class::Struct;
struct( Rusage => {
ru_utime => '@', # user time used
ru_stime => 'Timeval', # system time used
});
struct( Timeval => [
tv_secs => '$', # seconds
tv_usecs => '$', # microseconds
]);
# create an object:
my $t = Rusage->new(ru_utime=>[Timeval->new(), Timeval->new(), Timeval->new()], ru_stime=>Timeval->new());
# $t->ru_utime and $t->ru_stime are objects of type Timeval.
# set $t->ru_utime to 100.0 sec and $t->ru_stime to 5.0 sec.
$t->ru_utime->tv_secs(100);
$t->ru_utime->tv_usecs(0);
$t->ru_stime->tv_secs(5);
$t->ru_stime->tv_usecs(0);