sub dec2bin {
    my $str = unpack("B32", pack("N", shift));
#    $str =~ s/^0+(?=\d)//;   # otherwise you'll get leading zeros
    return substr( $str, -6 );
}

##</code><code>##

if( $value eq undef ) { ...

##</code><code>##

if( defined $value ) { ...

##</code><code>##

for my $i ( 0 .. 63 ) {
  ...
}

##</code><code>##

$tree->{ ('left', 'right')[ rand 2 ] }
       { ('left', 'right')[ rand 2 ] }
       { ('left', 'right')[ rand 2 ] } = 'AND';;