accessing hiCreateToggleField individual values

Hello, I have been struggling for a long time trying to figure out how this hiCreateToggleField works. I can't seem to figure out how to access individual items that are actually selected by the user. I put together a little testcase that I think will help me understand if you could modify it to "only" print what is selected in the form?

procedure(serdes_pop()
let((popWhat singleLib allLib libChoice labelField lib)

 mylist=list( list( 'MT1 "MT1" ) list( 'MT2 "MT2" ) )

     popWhat = hiCreateToggleField(
               ?name 'popWhat
               ?prompt "Populate:"
               ?choices mylist
               ?itemsPerRow 1
               )
  labelField = hiCreateLabel(
               ?name 'myLabel
               ?labelText "_________________________________________________"
               )
     popForm=hiCreateAppForm(
             ?name 'popFormdcr
             ?formTitle "Populate cadencelibs"
             ?callback 'popLib16CB
             ?fields list(popWhat labelField)
             ?unmapAfterCB t
               )
     hiDisplayForm(popForm)
  );endlet
 );endprocedure

procedure(popLib16CB(popForm)
prog((singleLib)
when(popForm
foreach(a popForm->popWhat->_toggleItems
print(symbolToString(a))
)
    )
    return(t)
))