in reply to Keeping the first occurence of a pattern, and removing the other occurences
Use a look-behind assertion to delete all occurrences that don't follow a store name heading.
s/(?<!===\n)DEPT:\s+PRODUCE\n+/\n/g;
Of course, I am assuming the input has UNIX-style line endings (newline character only). If not, you may need to replace "\n" with "\r\n" where appropriate.
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