Flushing expect_out(buffer)

Can some one tell me how to flush expect_out(buffer)?

below is my code

expect -re {.*} {}
expect "swpackages>*"
send  -i $con "trial.bat \r"
set outcome $expect_out(buffer)
expect "*continue*"
set prevreport $expect_out(buffer)
send "\r \r";

problem is :- I am getting "pre" stuffs in my buffer followed by the data I want :mad: