import BTL learn(1) lessons/editor

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diff --git a/usr.bin/learn/lib/editor/L35.2d b/usr.bin/learn/lib/editor/L35.2d
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+#print
+A useful operation is to replace a string of several blanks
+by exactly one blank.  Note that you can't just write
+
+s/ */ /
+
+because the " *" willl match any number of blanks
+including zero.  Thus it will always match at the beginning
+of the line, even if there is no blank there.
+The normal sequence is
+
+s/  */ /
+which will only substitute for a string
+that has at least one blank in it.
+Try that command on the line in the file "line".
+Then rewrite the file "line" and type "ready".
+#create Ref
+here is a long space.
+#create line
+here      is a long space.
+#user
+#cmp line Ref
+#log
+#next
+35.2e 5