Perl - Find and replace all

Find cpp and hpp recursively from the current directory then append those files onto the perl command, which substitutes "old" for "new" in those files while creating .bak backups.

find . -name "*.[ch]pp" -type f | xargs perl –i.bak –p –e 's/old/new/g;'

or non recursive:

perl -pi -w -e 's/search/replace/g;' *.php

-e means execute the following line of code.
-i means edit in-place
-w write warnings
-p loop