Find not used phrases?

[Robert9]

I could write a small script doing this:
open phrases.xml, fetch all phrase_names; prepare them if needed. (permissions, options);
run through all other files and try to find them; rename the original phrases to "name_123";
rebuild and see if there are any problems. If not I delete these phrases after a month or two.

Any better idea?
Find not used phrases?

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