sub consecutive_array {
    return scalar ( $_[0]..$_[-1] ) && 
# option:  ! grep { /\D/ } @_ &&    # checks for digits only
           join "_", @_ eq join "_", ($_[0]..$_[-1]);
}

#UPDATE, need to sort this array too to work, oops :-)
my @bigarray = sort map { ( $_->{array} ) } keys %hash;
my $valid = $bigarray[0] == 0 &&
            consectutive_array( @bigarray ) &&
            ! grep { !consectutive_array( $_->{array} ) } 
               keys %hash;