Certain word processors allow users to @link["http://practicaltypography.com/optional-hyphens.html"]{put soft hyphens} in their text. So consider whether it's possible that soft hyphens could appear in your input string.
It's also possible that soft hyphens could appear in your input string. Certain word processors allow users to @link["http://practicaltypography.com/optional-hyphens.html"]{insert soft hyphens} in their text.