I think Ithe most elegant solution is the eval so far. (Thanks for the other suggestions!) But I think I will combine the results of the suggestions, and will come up with a new Class, which will be returned if an undefined or nonexistent hash key has been found. So I will do module like this:

package TableMap::Undef;
use strict;

use overload
  "0+" => sub { return undef },
  "bool" = sub { return undef };

sub new{
  my $a={};
  my $x=shift;
  bltess ($a,ref($x)||$x);
  tie(%$a,"TableMap::Undef::TIE");
  return $a;
};

sub AUTOLOAD { return new TableMap::Undef; };

sub DESTROY {};

package TableMap::Undef::TIE;
use strict;

sub TIEHASH {
  my $a={};
  my $x=shift;
  bless ($a,ref($x)||$x);
  return $x;
};

sub FETCH { return new TableMap::Undef; };
[download]

Every time I need to return an undef I will return "new TableMap::Undef". This object is treated as undef as bool and numeric value, so this will cause right results when we test the value. This problem wuold be solved with a new perl pseudo-variable, we can call it $LAST for example, this is the value of the last similar level tag in the current expression. For example, I want to do things like this:

my $x=$s->{db} && $LAST->{users} && $LAST->{$user_id_1} && $LAST->limi
+ts && $LAST->{$user_id_2};
[download]

What do you think about it? Will it be a good feature request in perl6?

---

---

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:

  <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>

• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.