# AUTOLOAD is used to 
#  1) 'autoload' constants from the constant() function in ABC.xs  
# If the name is not a constant then it's parsed for 
#  2) a tie package-name::function-name, which if matched is executed

our $AUTOLOAD;  # implicit argument of AUTOLOAD

sub AUTOLOAD {

    my $constname;
    ($constname = $AUTOLOAD) =~ s/.*:://;
    my $val = constant($constname, 0);
    
    if ($!) {
        # the name in $AUTOLOAD is not a constant defined by XYZ::ABC
        if (my ($kind, $nolock, $function) = 
            $AUTOLOAD =~ /^XYZ::ABC::(Scalar|Array|Hash)::(NoLock::)?([A-Z]+)$/) {
            
            if ($function =~/^TIE$kind$/i) {
                my $self = shift;
                my $sah  = shift; # sah = scalar/array/hash
                return bless \$sah, $self;
                
                                   # vv Scalar or Array or Hash
            } elsif ($function =~ /^(FETCH|STORE)$/
                  || $kind !~ /^S/ # vv Array or Hash
                  && $function =~ /^(DELETE|EXISTS|CLEAR)$/
                  || $kind =~ /^A/ # vv Array
                  && $function =~ /^(FETCHSIZE|STORESIZE|EXTEND|POP|PUSH|SHIFT|UNSHIFT|SPLICE)$/
                  || $kind =~ /^H/ # vv Hash
                  && $function =~ /^(FIRSTKEY|NEXTKEY|SCALAR)$/) {
                  
                my $subname = 'abc' . ($nolock ? 'a_' : '_') . lc($kind) . '_' . lc($function);
                my $sah_ref = shift;
                {   no strict 'refs';
                
                    # differentiate subs with and without return values 
                    if ($function =~ /^(ST|CL|PU|UN|EXT)/) {
                        &$subname ($$sah_ref, @_);
                        return;
                    } else {    
                        return &$subname ($$sah_ref, @_);
                }   }
                
            } elsif ($function =~ /^(UNTIE|DESTROY)$/) {
                # how do we do nothing?
                return;  # ??
        }   }
        croak "$AUTOLOAD is not a defined constant or subroutine for XYZ::ABC";
    }
    # the name in $AUTOLOAD is a constant defined by XYZ::ABC: define it for perl
    
    eval "sub $AUTOLOAD { $val }"; # can this be $constname rather than $AUTOLOAD?
    goto &$AUTOLOAD; # can this just be 'return' if all of the defined names really are constants?
}