Variable updating when another variable changes. How to keep it static?

Question

I'm missing something very basic here I think. What's happening is that I'm looping through a list. I also need to update that list, but since I don't want to update the list I'm looping through, I created a temporary list to hold the new values. Then after I'm done looping, I'll update my original list with my temporary list.
I started out by defining/setting the variables:
<defvar name='matchedAccessLevels'>
     <ref>
          <concat>
               <s>user.accounts[FACILITIES].properties.locationMap[</s>
               <ref>theLoc</ref>
               <s>].accessLevels</s>                                                            
          </concat>                                                       
     </ref>                                                       
</defvar>
<defvar name='tempAccessLevels'>
     <ref>matchedAccessLevels</ref>                    
</defvar>Then I loop through. Below are the results from the log with block trace. It looks like whenever I update tempAccessLevels, it's updating matchedAccessLevels. The whole point of using tempAccessLevels was so that matchedAccessLevels remained static. What am I missing? What do I need to do differently to keep matchedAccessLevels from changing? I've tried many different combinations of code and still matchedAccessLevels is changing whenever I update tempAccessLevels.
<cond>
     <eq>
       <ref>theLoc</ref> --> Milwaukee
       <s>Milwaukee</s> --> Milwaukee
     </eq> --> 1
     <block trace='true'>
       <set name='matchedAccessLevels'>
          <ref>
            <concat>
               <s>user.accounts[FACILITIES].properties.locationMap[</s> --> user.accounts[FACILITIES].properties.locationMap[
               <ref>theLoc</ref> --> Milwaukee
               <s>].accessLevels</s> --> ].accessLevels
            </concat> --> user.accounts[FACILITIES].properties.locationMap[Milwaukee].accessLevels
          </ref> --> [Mail Room, Provider Audit File - Door 3142, Cost Reports - Door 3127]
       </set> --> null
       <set name='tempAccessLevels'>
          <ref>matchedAccessLevels</ref> --> [Mail Room, Provider Audit File - Door 3142, Cost Reports - Door 3127]
       </set> --> null
       <dolist name='theAccessLevel'>
          <ref>matchedAccessLevels</ref> --> [Mail Room, Provider Audit File - Door 3142, Cost Reports - Door 3127]
          <cond>
            <eq>
               <ref>theAccessLevel</ref> --> Mail Room
               <s>Mail Room</s> --> Mail Room
            </eq> --> 1
            <block trace='true'>
               <remove name='tempAccessLevels'>
                 <s>Mail Room</s> --> Mail Room
               </remove> --> null
               <ref>tempAccessLevels</ref> --> [Provider Audit File - Door 3142, Cost Reports - Door 3127]
               <ref>matchedAccessLevels</ref> --> [Provider Audit File - Door 3142, Cost Reports - Door 3127]
               <append name='tempAccessLevels'>
                 <s>Center Hall to NGS Far N Dr</s> --> Center Hall to NGS Far N Dr
               </append> --> null
               <ref>tempAccessLevels</ref> --> [Provider Audit File - Door 3142, Cost Reports - Door 3127, Center Hall to NGS Far N Dr]
               <ref>matchedAccessLevels</ref> --> [Provider Audit File - Door 3142, Cost Reports - Door 3127, Center Hall to NGS Far N Dr]
               <defvar name='isAccessLevelUpdated'>
               </defvar> --> null
            </block> --> null
          </cond> --> null

Answer 1

Ok, xpress objects are really Java objects and, as in Java, are handled by reference.
When you are setting tempAccessLevels, you are setting it to refer to the same list object as matchedAccessLevels.
A convenient way to actually copy a list is with the append function. eg:
<defvar name='tempAccessLevels'>
<append>
     <ref>matchedAccessLevels</ref>     
</append>               
</defvar>