@a1 = (1, 2, 3);
@a2 = ...;
@a3 = ...;
@a4 = ...;

$some_hash{$some_key} = [ \@a1, \@a2, \@a3, \@a4 ];

print "First array, 2nd value: ";
print $some_hash{$some_key}->[0]->[1];   # 2