Using Token-mod for Healing Potion Macro

I found this that Aaron posted a while back on using Token-mod for a Healing Potion macro:

!token-mod {{
  --set
    bar1_value|[[{@{target|Target|bar1}+2d4+2, @{target|Target|bar1|Max}d1}kl1]]
  --report
    all|"{name} takes a healing potion and regains {bar1_value:change}hp."
    gm:control|"{name} change: {bar1_value:before}hp -> {bar1_value}hp (+{bar1_value:before}hp)"
  --ids
    @{target|Target|token_id}
}}

One, this sort of works.  The health bar change works and doesn't exceed hp_max, but the text is wrong. I tried to update it so that the hp change text was correct and to also remove the requirement to select a target and instead just apply the changes to the currently selected token.  But I'm failing miserably.  Can someone help point out what I'm doing wrong here?

!token-mod {{
  --set
    bar1_value|[[{{bar1_value}+2d4+2, {bar1|Max}d1}kl1]]
  --report
    all|"{name} takes a healing potion and regains [[{{bar1_value}-{bar1_value:before}}]]hp."
    gm:control|"{name} hp change: {bar1_value:before} -> {bar1_value} (+[[{{bar1_value}-{bar1_value:before}}]])"

}}

This should work:

!token-mod {{
  --set
    bar1_value|[[{{@{selected|bar1_value}+2d4+2, @{selected|{bar1|Max}d1}kl1]]
 --report
    all|"{name} takes a healing potion and regains [[{{bar1_value}-{bar1_value:before}}]]hp."
    gm:control|"{name} hp change: {bar1_value:before} -> {bar1_value} (+[[{{bar1_value}-{bar1_value:before}}]])"
}}

I've actually made this a bit easier, try:

!token-mod {{
  --set
    bar1_value|+[[2d4+2]]!
 --report
    all|"{name} takes a healing potion and regains {bar1_value:abschange}hp."
    gm:control|"{name} hp change: {bar1_value:before} -> {bar1_value} (+{bar1_value:abschange}hp)"
}}

The ! on the end of the adjustment tells it to bound it to the range of the bar being changed. 

Excellent!  Thanks guys.  I did try @{selected, but I guess I didn't have the syntax correct.  But Aaron's ! to limit the change to the bar max automatically and the abschange works to show the delta.  Much appreciated!  The token-mod part of this macro works great now. 

I've added the resource reduction and a message to show how many are left. 

!modattr --silent --name @{selected|token_name} --repeating_resource_$0_resource_right|-1
!token-mod {{
  --set
    bar1_value|+[[2d4+2]]!
 --report
    all|"{name} takes a healing potion and regains {bar1_value:abschange}hp."
    gm:control|"{name} hp change: {bar1_value:before} -> {bar1_value} (+{bar1_value:abschange}hp)"
}}
/w gm @{selected|token_name} has [[@{selected|repeating_resource_$0_resource_right}-1]] healing potions left

Now, is there any way to check whether the current resource value is >0 (meaning they have a potion to take)? Like adding a 

if @{selected|repeating_resource_$0_resource_right}>0 then

I see that chatsetattr has the --evaluate flag which may accomplish this.  Or would this just have to be manually monitored through the resource quantity output?