By one-liners I meant things like Perl one-liners: perl -pe 's{<b>([^<]+)</b>}{<em>\1</em>}g' < foo.html > out.html Python would never let you get away wi

By one-liners I meant things like Perl one-liners: perl -pe 's{<b>([^<]+)</b>}{<em>\1</em>}g' < foo.html > out.html Python would never let you get away with treating it like an improved sed.