interaction between tr and s (was Re: tr question -- probably wrong list to ask, but ...)

Okay, given the following (without all the debugging code I had in  
earlier):

> # The code that grabs the parameters:
>
> my $qString = $ENV{'QUERY_STRING'};
> my @list = split( '&', $qString, 10 );
> my %queries = ();
> foreach my $pair ( @list )
> {	my ( $key, $value ) = split( '=', $pair, 2 );
> 	$key =~ s/%([\dA-Fa-f][\dA-Fa-f])/pack ("C", hex ($1))/eg;
> 	
> 	$value =~ tr/+/ /;
> 	
> 	$value =~ s/%([\dA-Fa-f][\dA-Fa-f])/pack ("C", hex ($1))/eg;

> 	$queries{ $key } = $value;
> }

Anyone know why commenting out the transliteration will recover the  
shift-JIS characters from the url-encoded stream (leaving spaces as  
'+', of course), but leaving the transliteration in will induce the  
code to drop shift-JIS lead bytes and every now and then whole  
characters?

I had a similar problem with

     $value =~ s/\+/ /g;

but it was an intermittent problem. (Haven't tried it today to see  
whether it only kills the shift-JIS characters when there is 8-bit  
space in the stream, but that may have been what was happening.)

Joel Rees
(waiting for a 3+GHz ARM processor to come out,
to test Steve's willingness to switch again.)