/usr/bin/hfst-twolc is in hfst 3.10.0~r2798-3.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
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#!/bin/sh /usr/bin/htwolcpre1 $@ | /usr/bin/htwolcpre2 $@ | /usr/bin/htwolcpre3 $@