Sub Articulo 76.2
Right. If you look at it in the right way, this is like doing
footnotes when you want to make it possible to put anything
into a footnote. Therein lies the answer. The following is
simply a reworking of the plain footnote macro involving, in DEK's
words, some aftergroup trickery:
\def\obeylinesmode{% parameter #1 (the text) is read later
\makelines}
\def\makelines{\vbox\bgroup\obeylines% and/or \obeyspaces, \bf or whatever
\futurelet\next\lines}
\def\lines{\ifcat\bgroup\noexpand\next \let\next\llines
\else\let\next\lnes\fi \next}
\def\llines{\bgroup\aftergroup\lllines\let\next}
\def\lnes{\lllines}
\def\lllines{\egroup}
\obeylinesmode{Ithink that I shall never see
A thing as lovely
As a flea.}