Exporting arrays

[Adam Spiers <adam@xxxxxxxxxxxxxxxxxxxxxxx>]

% foo=(a b c)
% typeset | grep zzz
array foo=(a b c)
% export foo=(a b c)
% typeset | grep zzz 
array exported foo=(a b c)

However,

% unset foo
% export foo=(a b c)
% typeset | grep zzz 
exported foo='(a b c)'

Presumably there's a decent reason for this behaviour; would
someone be good enough to explain it to me?