To return the first element of a pair:

Use the [pair->first] method. The following example iterates through an array of pairs and returns the first element from each.

Code

var( someGuy = array( 'First Name' = 'John', 'Last_Name' = 'Doe', 'Sex' = 'Male', 'Height' = '188cm') )

with p in $someGuy
     do => {^
          #p->first+'\n'
     ^}

Result

First Name
Last_Name
Sex
Height