Another way. Distinguishes undefined from non-existent keys (may be surplus to requirements). Needs 5.10+ for the  // defined-or operator.

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]'
'???'
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