c:\@Work\Perl\monks>perl -wMstrict -le "use 5.010; ;; my @AoH = ( { name => 'Adam', age => 0, }, { name => 'Bob', age => 10, }, { name => 'Cat', age => 20, }, { name => '0', age => 30, }, { name => 0, age => 35, }, { name => '', age => 40, }, { name => undef, age => 50, }, { age => 60, }, ); ;; my @empty; ;; print make_csv('name', @AoH); print make_csv('name', @empty); print make_csv('name'); print make_csv(); print make_csv('name', { name => 'Foo', age => 91, }); print make_csv('name', { name => '0', age => 92, }); print make_csv('name', { name => 0, age => 93, }); print make_csv('name', { name => '', age => 94, }); print make_csv('name', { name => undef, age => 95, }); print make_csv('name', { age => 96, }); ;; sub make_csv { my $k = shift; return qq{'@{[ join q{','}, map exists $_->{$k} ? $_->{$k} // '[UNDEF]' : '???', @_ ]}'}; } " 'Adam','Bob','Cat','0','0','','[UNDEF]','???' '' '' '' 'Foo' '0' '0' '' '[UNDEF]' '???'