Why does not work

[Wagner Jean-Jacques]

Why srcipt 1) is not working and script 2) does

1)
on mouseup
   put propertynames() into Var
  answer the number of lines of Var
end mouseup

2)
on mpuseup
  answer the number of lines of propertynames()
end mouseup


Is this a bug or a feature?
thanks
Jean-Jacques Wagner