Given — \catcode 9 = 9
\let ~ = \undefined ^^I~ \end why does XeTeX report This is XeTeX, Version 3.141592653-2.6-0.999993 (TeX Live 2021/W32TeX) (preloaded format=xetex) restricted \write18 enabled. entering extended mode (./untitled-10.tex ! Undefined control sequence. l.3 ^^I~ ? This output makes it appear that the offending control sequence is (or might be) ^^I~, whereas it is in fact simply ~. Should not the ^^I have been ignored rather than reported, as per line 1 ? Note line 3 does not really contain ^^I~ but rather <tab>~, but as tabs cannot be reliably included in e-mail I represent them here as ^^I. The ^^I in the transcript is genuine. -- Philip Taylor This email, its contents and any attachments are intended solely for the addressee and may contain confidential information. In certain circumstances, it may also be subject to legal privilege. Any unauthorised use, disclosure, or copying is not permitted. If you have received this email in error, please notify us and immediately and permanently delete it. Any views or opinions expressed in personal emails are solely those of the author and do not necessarily represent those of Royal Holloway, University of London. It is your responsibility to ensure that this email and any attachments are virus free.
