「Child Tree」のクッキーの処理は次のようなコードに
なっているようですが、エスケープ処理は行われていない
ようですね。PHP は自動処理してくれるとかあるようです
が、ブラウザも自動処理してくれるものもあるのかな？
Perl の場合、unpack pack しないといけないようです。

http://www.tohoho-web.com/wwwcook.htm

#--------------------------------------------------------------------------------------------------------------------
# [cookie発行]
# -> cookieを発行する(set_)
#
sub set_ {
if($_[0] eq "I"){$kday=1826;}else{$kday=30;}
($secg,$ming,$hourg,$mdayg,$mong,$yearg,$wdayg,$ydayg,$isdstg) = gmtime(time + $kday*24*60*60);
$yearg += 1900;
if($secg  < 10){$secg ="0$secg"; }
if($ming  < 10){$ming ="0$ming"; }
if($hourg < 10){$hourg="0$hourg";}
if($mdayg < 10){$mdayg="0$mdayg";}
$month = ('Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec')[$mong];
$youbi = ('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday')[$wdayg];
$date_gmt = "$youbi, $mdayg\-$month\-$yearg $hourg:$ming:$secg GMT";
if($SEL_C){$Csel=",sel:$sel";}else{$Csel="";}
if($TXT_C){$Ctxt=",txt:$txt";}else{$Ctxt="";}
$cook="name\:$name\,email\:$email\,url\:$url\,delkey\:$delkey\,pub\:$FORM{'pub'}\,ico\:$CICO\,font\:$font\,hr\:$hr$Csel$Ctxt";
if($_[0] eq "P"){print"Set-Cookie: $s_pas=$s_pas; expires=$date_gmt\n";}
elsif($_[0] eq "M"){print"Set-Cookie: Cmin=$FORM{'min'}; expires=$date_gmt\n";}
elsif($_[0] eq "I"){print"Set-Cookie: UID=$_[1]; expires=$date_gmt\n";}
else{print "Set-Cookie: CBBS=$cook; expires=$date_gmt\n";}
}
#--------------------------------------------------------------------------------------------------------------------
# [cookie取得]
# -> cookieを取得する(get_)
#
sub get_ { 
$cookies = $ENV{'HTTP_COOKIE'};
@pairs = split(/;/,$cookies);
foreach $pair (@pairs) {
	($NAME, $value) = split(/=/, $pair);
	$NAME =~ s/ //g;
	$DUMMY{$NAME} = $value;
}
if($_[0] eq "P"){if($DUMMY{"$s_pas"}){$FORM{"P"}=$DUMMY{"$s_pas"};}}
elsif($_[0] eq "M"){if($DUMMY{'Cmin'}){$FORM{"min"}=$DUMMY{'Cmin'};}else{$FORM{"min"}=0;}}
elsif($_[0] eq "I"){if($DUMMY{'UID'}){$pUID=$DUMMY{'UID'};}else{$pUID="n";}}
else{
	@pairs = split(/,/,$DUMMY{'CBBS'});
	foreach $pair (@pairs) {
		($name, $value)= split(/:/, $pair);
		$COOKIE{$name} = $value;
	}
	$c_name=$COOKIE{'name'};$c_email=$COOKIE{'email'};
	$c_url =$COOKIE{'url'}; $c_key  =$COOKIE{'delkey'};
	$c_pub =$COOKIE{'pub'}; $c_ico  =$COOKIE{'ico'};
	$c_font=$COOKIE{'font'};$c_hr   =$COOKIE{'hr'};
	if($SEL_C){$c_sel=$COOKIE{'sel'};}
	if($TXT_C){$c_txt=$COOKIE{'txt'};}
}
}
#-------------------------------------------------------------------------------------------------------------------

多遊さんのところでも前に使っていた BBS-TypeN 
ですが、
http://tayu.o0o0.jp/cgi-bin/bbs/bbs.cgi

こちらはオリジナルから私が相当改変したので
元々かどうかは忘れましたが、次のように
pack unpack していますね。
※自分のところのソースのタイムスタンプは
　2006-05-17 になっていました。15年も前か
　最終バージョンは…

# ■クッキーデータのデコード
#
sub CookieDecode
{
	foreach (split(/\;/, $ENV{'HTTP_COOKIE'})) {
		($Key, $Value) = split(/=/);
        $Value =~ s/%([0-9A-Fa-f][0-9A-Fa-f])/pack( "C", hex( $1 ) )/eg;
		$COOKIES{$Key} = $Value;
	}

	($COOKIE{'name'},
		$COOKIE{'mail'},
		$COOKIE{'url'},
		$COOKIE{'message_no'},
		$COOKIE{'text'},
		$COOKIE{'link'},
		$COOKIE{'vlink'},
		$COOKIE{'alink'},
		$COOKIE{'bgcolor'},
		$COOKIE{'background'},
		$COOKIE{'vertical_bar_width'},
		$COOKIE{'vertical_bar'},
		$COOKIE{'vertical_image'},
		$COOKIE{'horizon_bar'},
		$COOKIE{'horizon_image'},
		$COOKIE{'hrline'},
	) = split( /\"/, $COOKIES{$CGIName});

	if( $FORM{'function'} eq "write" )
	{
		$FORM{'name'} || ($COOKIE{'name'} = "");
		$FORM{'mail'} || ($COOKIE{'mail'} = "");
		$FORM{'url'} || ($COOKIE{'url'} = "");
	}
}
#------------------------------------------------------------------------------

#------------------------------------------------------------------------------
# ■クッキーの設定
#
sub CookieSet
{
	$MessageNo = scalar( @LogFile ) + ($HEAD{'log'} - 1) * $MaxLog;

	$FORM{'name'} ? $COOKIE{'name'} = $FORM{'name'} : $FORM{'name'} = $COOKIE{'name'};
	$FORM{'mail'} ? $COOKIE{'mail'} = $FORM{'mail'} : $FORM{'mail'} = $COOKIE{'mail'};
	$FORM{'url'} ? $COOKIE{'url'} = $FORM{'url'} : $FORM{'url'} = $COOKIE{'url'};
	$COOKIE{'text'} && ($Text = $COOKIE{'text'});
	$COOKIE{'link'} && ($Link = $COOKIE{'link'});
	$COOKIE{'vlink'} && ($VLink = $COOKIE{'vlink'});
	$COOKIE{'alink'} && ($ALink = $COOKIE{'alink'});
	$COOKIE{'bgcolor'} && ($BgColor = $COOKIE{'bgcolor'});
	$COOKIE{'background'} && ($BackGround = $COOKIE{'background'});
	$COOKIE{'vertical_bar_width'} && ($VerticalBarWidth = $COOKIE{'vertical_bar_width'});
	$COOKIE{'vertical_bar'} && ($VerticalBar = $COOKIE{'vertical_bar'});
	$COOKIE{'vertical_image'} && ($VerticalImage = $COOKIE{'vertical_image'});
	$COOKIE{'horizon_bar'} && ($HorizonBar = $COOKIE{'horizon_bar'});
	$COOKIE{'horizon_image'} && ($HorizonImage = $COOKIE{'horizon_image'});
	$COOKIE{'hrline'} && ($HRLine = $COOKIE{'hrline'});

	($Sec, $Min, $Hour, $MDay, $Mon, $Year, $WDay, $YDay, $Isdst) = gmtime(time + 30 * 24 * 60 * 60);
	$Year += 1900;
	$Mon = ('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec')[$Mon];
	$WDay = ('Sunday','Monday','Tuesday ','Wednesday','Thursday','Friday','Saturday')[$WDay];
	$Sec = "0$Sec" if $Sec < 10;
	$Min = "0$Min" if $Min < 10;
	$Hour = "0$Hour" if $Hour < 10;
	$MDay = "0$MDay" if $MDay < 10;

	$Value = join( "",
		"$FORM{'name'}",
		"\"$FORM{'mail'}",
		"\"$FORM{'url'}",
		"\"$MessageNo",
		"\"$Text",
		"\"$Link",
		"\"$VLink",
		"\"$ALink",
		"\"$BgColor",
		"\"$BackGround",
		"\"$VerticalBarWidth",
		"\"$VerticalBar",
		"\"$VerticalImage",
		"\"$HorizonBar",
		"\"$HorizonImage",
		"\"$HRLine" );

	$Value =~ s/(\W)/sprintf("%%%02X", unpack("C", $1))/eg;
	print "Set-Cookie: $CGIName=", $Value, "; expires=$WDay, $MDay-$Mon-$Year $Hour:$Min:$Sec GMT;\n";
}
#------------------------------------------------------------------------------