This is a version of the script that detects, adds and subtracts health points depending on the objects in the environment.

contagion.lsl

///////////////////////////////////////////////////////////////////////////
//  Copyright (C) Wizardry and Steamworks 2013 - License: GNU GPLv3      //
//  Please see: http://www.gnu.org/licenses/gpl.html for legal details,  //
//  rights of fair usage, the disclaimer and warranty conditions.        //
///////////////////////////////////////////////////////////////////////////
 
///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2011 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
string wasProgress(integer percent, integer length, list symbols) {
    percent /= (integer)((float)100.0/(length));
    string p = llList2String(symbols,0);
    integer itra = 0;
    do {
        if(itra>percent-1) p += llList2String(symbols,2);
        else p += llList2String(symbols,1);
    } while(++itra<length);
    return p + llList2String(symbols,3);
}
 
///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2013 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
vector wasPercentToGradient(float percent, string rgb) {
    if(llStringLength(rgb) != 2) {
        llSay(DEBUG_CHANNEL, "Assert failed, rgb parameter must consist of a pair of either r, g, or b.");
        return ZERO_VECTOR;
    }
    string a = llGetSubString(rgb, 0, 0);
    string b = llGetSubString(rgb, 1, 1);
    list col = [ "r", "g", "b" ];
    integer ax = llListFindList(col, (list)a);
    integer bx = llListFindList(col, (list)b);
    if(ax == -1 || bx == -1) {
        llSay(DEBUG_CHANNEL, "Asset failed, rgb parameters must contain either r, g, or b letters.");
        return ZERO_VECTOR;
    }
    col = llListReplaceList(col, (list)((100-percent)/100), ax, ax);
    col = llListReplaceList(col, (list)(percent/100), bx, bx);
    return 2*<llList2Float(col, 0), llList2Float(col, 1), llList2Float(col, 2)>;
}
 
///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2015 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
string wasKeyValueGet(string k, string data) {
    if(llStringLength(data) == 0) return "";
    if(llStringLength(k) == 0) return "";
    list a = llParseStringKeepNulls(data, ["&", "="], []);
    integer i = llListFindList(llList2ListStrided(a, 0, -1, 2), [ k ]);
    if(i != -1) return llList2String(a, 2*i+1);
    return "";
}
 
///////////////////////////////////////////////////////////////////////////
//    Copyright (C) 2012 Wizardry and Steamworks - License: GNU GPLv3    //
///////////////////////////////////////////////////////////////////////////
list wasDeleteSubListMatch(list in, string match) {
    if(llGetListLength(in) == 0) return [];
    string first = llList2String(in, 0);
    in = llDeleteSubList(in, 0, 0);
    if(llSubStringIndex(first, match) == -1) jump next;
    return wasDeleteSubListMatch(in, match);
@next;
    return first + wasDeleteSubListMatch(in, match);
}
 
// Quick function to list AoE.
string getEffects() {
    if(llGetListLength(effects)) return "Effects: " + "[ " + llDumpList2String(effects, ",") + " ]";
    return "";
}
 
integer health = 100;
list effects = [];
 
default
{
    state_entry() {
        llSetTimerEvent(1);
        llSensorRepeat("", "", ACTIVE|PASSIVE, 96, TWO_PI, 1);
    }
 
    // When an AoE objects are detected, go through all off them and process them.
    sensor(integer num) {
        --num;
        do {
            // First grab the formatted name.
            string data = llDetectedName(num);
            // If the range of the AoE is smaller than the distance between the AV and the 
            // trigger point, then remove the AoE effect from the effects list and continue.
            string dh = wasKeyValueGet("range", data);
            // If the object does not have a range set, it's not going to affect the avatar
            // and is most likely just a static object not part of the project. Quickly ignore.
            if(dh == "") jump continue;
            if(llVecDist(llGetPos(), llDetectedPos(num)) > (float)dh) {
                // AoE effect range does not reach us, delete it if in effects and continue.
                string name = wasKeyValueGet("name", data);
                if(llListFindList(effects, (list)name) != -1) {
                    effects = wasDeleteSubListMatch(effects, name);
                }
                jump continue;
            }
            // Check if the effect has a properly formatted name.
            dh = wasKeyValueGet("name", data);
            // If it doesn't ignore it, and jump to AoE processing.
            if(dh == "") jump effect;
            // If it does, add it to the list of AoE effects.
            if(llListFindList(effects, (list)dh) == -1) {
                effects += dh;
                jump effect;
            }
            // If the effect is already active, ignore the AoE (non-stacking AoE)
            return;
@effect;
            // Check if the effect has a properly formatted health.
            dh = wasKeyValueGet("health", data);
            // If it does not, ignore and continue and don't waste time.
            if(dh == "") jump continue;
            // Get the health and add it to the current health, either increasing or decreasing
            // while making sure that it doesn't underrun 0, respectively 100 (Hard cap).
            integer mod = (integer)dh;
            if(health + mod > 100) {
                health = 100;
                jump continue;
            }
            if(health + mod < 0) {
                health = 0;
                jump continue;
            }
            // It does not overstep, so just perform the arithmetic.
            health += mod;
@continue;
        } while(--num>-1);
    }
 
    // If no AoE objects are detected, consequently wipe the list.
    no_sensor() { effects = []; }
 
    // Restart the script on rez and attach to make sure that llGetOwner() returns a correct key (BUG)
    on_rez(integer num) { llResetScript(); }
    attach(key id) { llResetScript(); }
 
    // Every tick, display overhead status.
    timer() { llSetText("Health: " + wasProgress(health, 10, ["[", "█", "░", "]"]) + "\n" + getEffects(), wasPercentToGradient(health, "rg"), 1); }
 
}