Search & Replace using Perl command

Searches for all files recursively that contain <string2replace> (put any string you want here, this is just for my example) and prints out a list of just the filenames.
The xargs command then passes that list to perl. Our friend perl then does -p to run script on every line of the file, -i to edit in place, -e run the following script (input from command line), 's/???/!!!/g' replaces ??? with !!! and /g says to do it for multiple occurrences on the same line. Use the first command without -i and piped to less to just see an output of all the changes it will make if using -i just to check first. The -i does an inline replace and that is permanent (shows nothing on screen). Without the -i it sends the expected results to standard out (shows it on the screen) but doesn't actually do the change. Think of it as preview-mode.

First test it to see if it looks good.

$ grep -lr <string2replace> . | xargs -n1 perl -p -e 's/<string2replace>/<replacement>/g' | less

Do it for real.

$ grep -lr <string2replace> . | xargs -n1 perl -p -i -e 's/<string2replace>/<replacement>/g'

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