Quote

[xxx][yyy] # perl
sub a {return}
sub b {return 1 .. 3}

my %hash = (a => &a || "--NOT-DEFINED--", b => &b);

use Data::Dumper;
print STDOUT Dumper \%hash;

$VAR1 = {
'a' => '--NOT-DEFINED--',
'b' => 1,
'2' => 3
};
[yyy][xxx] #