# Autoattr.pm
package Autoattr;
our $DEBUG;
sub new($) {
    $DEBUG and printf STDERR "%s::new(%s)\n",
        __PACKAGE__, join ', ', map "'$_'", @_;
    ref $_[0] ? bless {%{$_[0]}}, ref $_[0] : bless {}, $_[0];
}
sub DESTROY {
    $DEBUG and printf STDERR "%s::DESTROY(%s)\n",
        __PACKAGE__, join ', ', map "'$_'", @_;
    return;
}
sub AUTOLOAD {
    no strict qw(refs);
    our $AUTOLOAD;
    $DEBUG and printf STDERR "%s::AUTOLOAD=%s(%s)\n",
        __PACKAGE__, $AUTOLOAD, join ', ', map "'$_'", @_;
    if ($AUTOLOAD =~ /:get_([^:]*)$/) {
        my $attr = $1;
        *{$AUTOLOAD} = sub {$_[0]->{$attr}};
    }
    elsif ($AUTOLOAD =~ /:set_([^:]*)$/) {
        my $attr = $1;
        *{$AUTOLOAD} = sub {$_[0]->{$attr} = $_[1]; $_[0]};
    }
    else {
        (my $get = $AUTOLOAD) =~ s/([^:]*)$/get_$1/;
        (my $set = $AUTOLOAD) =~ s/([^:]*)$/set_$1/;
        *{$AUTOLOAD} = sub {goto \&{$#_ ? $set : $get}};
    }
    goto \&$AUTOLOAD;
}
1;

##</code><code>##

#!/usr/bin/perl -w

package Foo;
use base qw(Autoattr);
sub get_foo {$_[0]->{foo} .= 'foo'}
sub set_bar {$_[0]->{bar} = 'bar' x $_[1]; $_[0]}

package Bar;
use base qw(Foo);

package main;
BEGIN {$Autoattr::DEBUG = 1}
$_ = Bar->new;
printf "\n>>> %s, %s, %s\n\n",
    $_->foo,
    $_->foo,
    $_->foo;
printf "\n>>> %s, %s, %s\n\n",
    do {$_->bar(3); $_->bar},
    do {$_->bar(2); $_->bar},
    do {$_->bar(1); $_->bar};

##</code><code>##

Autoattr::new('Foo')                                                            
Autoattr::AUTOLOAD=Foo::foo('Foo=HASH(0x225140)')                               
                                                                                
>>> foo, foofoo, foofoofoo                                                      
                                                                                
Autoattr::AUTOLOAD=Foo::bar('Foo=HASH(0x225140)', '3')                          
Autoattr::AUTOLOAD=Foo::get_bar('Foo=HASH(0x225140)')                           

>>> barbarbar, barbar, bar                                                      
                                                                                
Autoattr::DESTROY('Foo=HASH(0x225140)')                                         

##</code><code>##

Autoattr::new('Bar')                                                            
Autoattr::AUTOLOAD=Bar::foo('Bar=HASH(0x225164)')                               
Autoattr::AUTOLOAD=Bar::get_foo('Bar=HASH(0x225164)')                           
Use of uninitialized value in printf at C:\dev\perl\test.pl line 32.            
Use of uninitialized value in printf at C:\dev\perl\test.pl line 32.            
Use of uninitialized value in printf at C:\dev\perl\test.pl line 32.            
                                                                                
>>> , ,                                                                         
                                                                                
Autoattr::AUTOLOAD=Bar::bar('Bar=HASH(0x225164)', '3')                          
Autoattr::AUTOLOAD=Bar::set_bar('Bar=HASH(0x225164)', '3')                      
Autoattr::AUTOLOAD=Bar::get_bar('Bar=HASH(0x225164)')                           

>>> 3, 2, 1                                                                     
                                                                                
Autoattr::DESTROY('Bar=HASH(0x225164)')                                         

##</code><code>##

package Autoattr;
our $DEBUG;
sub new($) {
    $DEBUG and printf STDERR "%s::new(%s)\n",
        __PACKAGE__, join ', ', map "'$_'", @_;
    ref $_[0] ? bless {%{$_[0]}}, ref $_[0] : bless {}, $_[0];
}
sub DESTROY {
    $DEBUG and printf STDERR "%s::DESTROY(%s)\n",
        __PACKAGE__, join ', ', map "'$_'", @_;
    return;
}
sub AUTOLOAD {
    no strict qw(refs);
    $DEBUG and printf STDERR "%s::AUTOLOAD=%s(%s)\n",
        __PACKAGE__, our $AUTOLOAD, join ', ', map "'$_'", @_;
    *{$AUTOLOAD} =                                    # into the symbol table
        $AUTOLOAD =~ /(?<![^:])get_([^:]*)$/s ? do {  # define a getter
            my $attr = $1;
            sub($) {ref $_[0] ? $_[0]->{$attr} : ${"$_[0]::$attr"}};
        } :
        $AUTOLOAD =~ /(?<![^:])set_([^:]*)$/s ? do {  # define a setter
            my $attr = $1;
            sub($$) {
                ref $_[0] ? $_[0]->{$attr} : ${"$_[0]::$attr"} = $_[1];
                $_[0];
            };
        } : do {                                      # get/set depending on @_
            (my $get = $AUTOLOAD) =~ s/([^:]*)$/get_$1/;
            (my $set = $AUTOLOAD) =~ s/([^:]*)$/set_$1/;
            sub($;$) {$#_ ? $_[0]->$set(@_[1 .. $#_]) : $_[0]->$get};
        }
    ;
    $AUTOLOAD =~ /([^:]*)$/; goto $_[0]->can($1);     # go to the new symbol
}