( a ( a ( a ( a ( aa ) a ) a ) a ) a ) 

##</code><code>##

#! perl -slw
use strict;

sub recurse {
	print ">> '${ $_[ 0 ] }'";
	if( length ${ $_[ 0 ] } ) {
		recurse( \ substr( ${ $_[ 0 ] }, 1, -1 ) );
		${ $_[ 0 ] } = " ( ${ $_[ 0 ] } ) ";
	}
	print "<< '${ $_[ 0 ] }'";
	return;
}

my $str = 'aaaaaaaaaa';
recurse \$str;

print $str;
__END__
P:\test>junk
>> 'aaaaaaaaaa'
>> 'aaaaaaaa'
>> 'aaaaaa'
>> 'aaaa'
>> 'aa'
>> ''
<< ''
<< ' ( aa ) '
<< ' ( aaaa ) '
<< ' ( aaaaaa ) '
<< ' ( aaaaa'
<< ' ( a ( aaaaaaaa ) a ) '
 ( a ( aaaaaaaa ) a )