use Config::Tiny;

my $conf = Config::Tiny->read('your_config');

my $debug = $conf->{_}->{debug};
my $routers = $conf->{routers}; # Hash ref with routers information
my $groups = $conf->{groups}; # Hash ref with group information

my $router1 = $routers->{router1}; # Router's IP
my $group1 = $groups->{group1}; # Array ref with routers list which belong to group 1.

. . .