Info on MS Word Variables, look here
http://msdn2.microsoft.com/en-us/library/aa212463(office.11).aspx

So, in Word's object modell, the Variables collection is hosted in the
Document object which itself is hosted under the Word.Application object
Below (immediate window) sequence examplifies this

set d = word.ActiveDocument
set v = d.Variables.Add(Name:="Temp", Value:="12")
? d.variables(1)
12

Since I'm not a Perl developer, you'll have to translate the above
info to Perl.

Krgrds,
Perry