perl -i -pe 's/\.mbh_succ_roam_i_vlr_e_plmn\s/\.new_mbh_succ_roam_i_vlr_e_plmn/g' <input_file>

##</code><code>##

perl -i -pe 's/\.mbh([_a-z]+)\s/\.new$1/g' < input_file