one line perl search replace

current directory

perl -p -i -e 's/oldstring/newstring/g' *

recursive

perl -p -i -e 's/oldstring/newstring/g' `find ./ -name *.html`

do the replace only on flies we know to contain the original string

perl -p -i -e 's/oldstring/newstring/g' `grep -ril oldstring *`