An example of optional parameters inside handlers using lists or records. From the AppleScript Users list

OS version: OS X

Applescript:

processArgs({1, 2, 3})
--> 30
processRecord({a:1, b:2, c:3})
--> {3,5}

on processArgs(args)
set x to 5
repeat with arg in args
set x to x * arg
end repeat
end processArgs

on processRecord(hash)
set len to count hash as list
set x to 5
try
set x to x + (d of hash)
end try
return {len, x}
end processRecord