Document alternative delimiters for substitution, from Jim Wisniewski.

tmux.1

@@ -5080,6 +5080,15 @@ would change
 .Ql abABab
 into
 .Ql bxBxbx .
+A different delimiter character may also be used, to avoid collisions with
+literal slashes in the pattern.
+For example,
+.Ql s|foo/|bar/|:
+will substitute
+.Ql foo/
+with
+.Ql bar/
+throughout.
 .Pp
 In addition, the last line of a shell command's output may be inserted using
 .Ql #() .