my $a; print "my \$a;\n";
print "Undefined\n" unless defined $a;
print "False\n" unless $a;

$a=0; print "\nmy \$a=0;\n";
if (defined $a) {
    print "Defined\n";
} else {
    print "Undefined\n";
}
if ($a) {
    print "True\n";
} else {
    print "False\n";
}

$a=''; print "\nmy \$a='';\n";
print eval'(defined $a) ? "Defined\n" : "Undefined\n"';
print eval'($a) ? "True\n" : "False\n"';

$a=1; print "\nmy \$a=1;\n";
print ((defined $a) ? "Defined\n" : "Undefined\n");
print (($a) ? "True\n" : "False\n");

$a='foo';print "\nmy \$a='foo';\n";
print '',(defined $a) ? "Defined\n" : "Undefined\n";
print '',($a) ? "True\n" : "False\n";

undef $a; print "\nundef \$a;\n";
(defined $a) ? print "Defined\n" : print "Undefined\n";
($a) ? print "True\n" : print "False\n";

##</code><code>##

print (defined $a) ? "Defined\n" : "Undefined\n";