I found a similar issue. EiffelStudio's editor gets confused after a string of the form "foo bar %%". Adding a space after the second % (before the closing ") solves the problem, but the string is not what I want.

I found two workarounds:

"foo bar %/25/"
"foo bar" + ('%%').out

I'm happy with neither of them, because they make the code more difficult to read than it was before.
Using a verbatim string would mean 3 lines, which is too verbose.

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Eric Bezault