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-- which I did not find a way for to encapsulate it within a function -- I'd like to add a simple version, which is partly based on Richard Hansen's answer, but does address also the pitfall that occurs with an empty array=():

-- which I did not find a way for to encapsulate it within a function -- I'd like to add a simple version, which is partly based on Richard Hansen's answer, but does address also the pitfall that occurs with an empty array=():

a; # is not declared a=; # is declared a="foo"; # is declared a=(); # is declared a=(""); # is declared unset a; # is not declared a; # is unset a=; # is not unset a="foo"; # is not unset a=(); # is not unset a=(""); # is not unset unset a; # is unset 

a; # is not declared a=; # is declared a="foo"; # is declared a=(); # is declared a=(""); # is declared unset a; # is not declared a; # is unset a=; # is not unset a="foo"; # is not unset a=(); # is not unset a=(""); # is not unset unset a; # is unset