defined(mytest()) is defined.
mytest() is false.
mytest() returns: ''

defined($out[2]) is defined.
$out[2] is false.
$out[2] returns: ''

defined(if(0>1){1}) is defined.
if(0>1){1} is false.
if(0>1){1} returns: ''

defined(do{}) returns: an undefined value.

defined((map{if(0>1){1}}(1))[0]) is defined.
(map{if(0>1){1}}(1))[0] is false.
(map{if(0>1){1}}(1))[0] returns: ''

defined((map{$_=$hash{$_};if($_>50){$max=$_}}keys %hash)[2]) is defined.
(map{$_=$hash{$_};if($_>$max){$max=$_}}keys %hash)[2] is false.
(map{$_=$hash{$_};if($_>$max){$max=$_}}keys %hash)[2] returns: ''