use strict;
use warnings;

use Data::Dumper; 

my %hash=(1=>10,2=>20,3=>30,4=>40,5=>50);


my $max=0;
my @out=map{
    $_=$hash{$_};
    if($_>$max){$max=$_}
#    $_;
}keys %hash;


sub mytest { if ( 0 > 1 ) { 1; } }


print "defined(mytest()) is ", 
      defined( mytest() ) 
          ? "defined.\n" 
          : "undefined.\n";
print "mytest() is ",
      mytest()
          ? "true.\n"
          : "false.\n";
print "mytest() returns: '", mytest(), "'\n\n";



print "defined(\$out[2]) is ",
      defined( $out[2] )
          ? "defined.\n"
          : "undefined\n";
print "\$out[2] is ",
      $out[2]
          ? "true.\n"
          : "false.\n";
print "\$out[2] returns: '", $out[2], "'\n\n";



print "defined(if(0>1){1}) is ",
      defined( do{ if(0>1){1} } )
          ? "defined.\n"
          : "undefined.\n";
print "if(0>1){1} is ",
      do{ if(0>1){1} }
          ? "true.\n"
          : "false.\n";
print "if(0>1){1} returns: '",
      do{ if(0>1){1} },
      "'\n\n";


print "defined(do{}) returns: ", 
      defined( do{} )
          ? "a defined value.\n\n"
          : "an undefined value.\n\n";


print "defined((map{if(0>1){1}}(1))[0]) is ",
      defined((map{if(0>1){1}}(1))[0])
          ? "defined.\n"
          : "undefined.\n";
print "(map{if(0>1){1}}(1))[0] is ",
      (map{if(0>1){1}}(1))[0]
          ? "true.\n"
          : "false.\n";
print "(map{if(0>1){1}}(1))[0] returns: '",
      (map{if(0>1){1}}(1))[0],
      "'\n\n";


print "defined((map{\$_=\$hash{\$_};if(\$_>$max){\$max=\$_}}keys %hash)[2]) is ",
      defined((map{$_=$hash{$_};if($_>$max){$max=$_}}keys %hash)[2])
          ? "defined.\n"
          : "undefined.\n";
print "(map{\$_=\$hash{\$_};if(\$_>\$max){\$max=\$_}}keys %hash)[2] is ",
      ( do{map{$_=$hash{$_};if($_>$max){$max=$_}} keys %hash} )[2]
          ? "true.\n"
          : "false.\n";
print "(map{\$_=\$hash{\$_};if(\$_>\$max){\$max=\$_}}keys %hash)[2] returns: '",
      (map{$_=$hash{$_};if($_>$max){$max=$_}} keys %hash)[2],
      "'\n\n";

##</code><code>##

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: ''