/usr/share/doc/calcurse/ru/pipe.txt is in calcurse 4.2.1-1.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 | Pipe
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Pipe the selected item to an external program.
Press the '|' key to pipe the currently selected appointment or todo entry to
an external program.
You will be driven back to calcurse as soon as the program exits.
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