4.3BSD-Tahoe/usr/lib/learn/eqn/L5.1b

#once #create message
.ND
.EQ
delim $$
.EN
.LP
The problem is really that we need a way to tell neqn
that in spite of blanks, a group of things (like the $pi$
and the +1) have to be kept together as a single superscript.
The way that this is done is to enclose the group in
braces - the characters { and } - like this:

  .EQ
  x sup {pi + 1}
  .EN

This tells neqn that everything inside the braces belongs
to the superscript, in spite of blanks and tildes.
(You don't need blanks before and after braces themselves -
like tildes, they act as delimiters.)

Modify the file "Example" so that the output looks like
the following, then type "ready".
(To get $==$, type ==.)
.pl 1
#once #create Ref
.LP
.EQ
x sup {pi +1} == y sup z sup {alpha + beta}
.EN
.pl 1
#once #create Example
.LP
.EQ
replace me
.EN
.pl 1
#
#once neqn Ref | nroff >X1 &
#once neqn message Ref | nroff -T$term %s/tinyms -
#user
neqn Example | nroff >X2
#cmp X1 X2
#log
#next
5.1c 10
5.2b 5