Put, undo and redo: p, P, u and <C-r>

4 drills

1. Fix a typo with xp: Two letters are swapped. The cursor is on the first of them. Swap them back.
2. Swap two lines: The line under the cursor should come after the next one. Swap them.
3. Move a line to the top: This line belongs at the very top of the file. Cut it and put it above the first line.
4. Duplicate a line, then edit it: Copy the line below itself, then change one word in the copy to match the target.

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