wpub pwub wupb uwpb puwb upwb wpbu pwbu wbpu bwpu pbwu bpwu wubp uwbp wbup bwup ubwp buwp pubw upbw pbuw bpuw ubpw bupw
Note: these 'words' (valid or invalid) are all the permutations of the word wpub. These words are obtained by scrambling the letters in wpub.