See Template::Manual::VMethods, and create a custom virtual method called , isa, and use it like

[% IF variable.isa('HASH') %]
   [% FOREACH pair in variable.pairs %]
   KEY: [% pair.key %] VALUE: [% pair.value %] 
   [% END %]
[% ELSIF variable.isa('ARRAY') %]
   [% FOREACH item in variable %]
   ITEM: [% item %]
   [% END %]
[% ELSE %]
   [% variable %]
[% END %]
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