Cmake's foreach command includes forms
foreach(<loop_var> IN LISTS <lists>)
foreach(<loop_var> IN ITEMS <items>)
foreach(<loop_var> RANGE ...)
We get the lines to be parsed by
file(STRINGS "${filepath}" lines)
If in the parsed lyx-file there is a line
containing only the single word 'IN', or 'RANGE', then
the command
foreach(_l ${lines})
can create a syntax error (at least with cmake1.16)
In fact, in file pl_Additional.lyx:12913 happens to have
such a beast.