Given:
$delim2 = 'A -4 B';
$set->{'key2'} => ['A -4 B','B -4 C','C -4 A','A -4 B'],

RESULT:
[A -4 B]    #ok
[A -4 B]    #ok
[A -4 B] [B -4 C] [C -4 A] [A -4 B] #ok
[A -4 B]       #not ok -- don't know how this is obtained