$ perl -le '$_ = q{Dr P J van Houten MD}; > s[(?<=[A-Z])(?=\s)][.]g; > print;' Dr P. J. van Houten MD $ perl -le '$_ = q{Dr P J van Houten MD FRCS}; > s[(?<=[A-Z])(?=\s)][.]g; > print;' Dr P. J. van Houten MD. FRCS $ #### $ perl -le '$_ = q{Dr P J van Houten MD FRCS}; > s{(?:(?<=\A[A-Z])|(?<=\s[A-Z]))(?=\s)}{.}g; > print;' Dr P. J. van Houten MD FRCS $