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-rw-r--r--Doc/Zsh/expn.yo9
1 files changed, 9 insertions, 0 deletions
diff --git a/Doc/Zsh/expn.yo b/Doc/Zsh/expn.yo
index a75513b25..60c74cab1 100644
--- a/Doc/Zsh/expn.yo
+++ b/Doc/Zsh/expn.yo
@@ -340,6 +340,15 @@ process.  This may be used instead of the tt(<)
 form for a program that expects to lseek (see manref(lseek)(2))
 on the input file.
 
+There is an optimisation for substitutions of the form
+tt(=LPAR()<<<)var(arg)tt(RPAR()), where var(arg) is a single-word argument
+to the here-string redirection tt(<<<).  This form produces a file name
+containing the value of var(arg) after any substitutions have been
+performed.  This is handled entirely within the current shell.  This is
+effectively the reverse of the special form tt($LPAR()<)var(arg)tt(RPAR())
+which treats var(arg) as a file name and replaces it with the file's
+contents.
+
 The tt(=) form is useful as both the tt(/dev/fd) and the named pipe
 implementation of tt(<LPAR())var(...)tt(RPAR()) have drawbacks.  In 
 the former case, some programmes may automatically close the file