Add a bit about spaces in opt_VARS values.

[wblock]

en_US.ISO8859-1/books/porters-handbook/makefiles/chapter.xml

4493 ↗

(On Diff #13740)

To avoid the if/pause/then, how about:

Values containing whitespace must be enclosed in quotes:

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(On Diff #13740)

s/because of/due to/

4498 ↗

(On Diff #13740)

How about:

expansion deals with whitespace.  When
<literal>OPT_VARS= foo=bar baz</literal> is expanded,
the variable ends up containing two strings,
<literal>foo=bar</literal> and <literal>baz</literal>.
But the submitter probably intended there to be only one string,
<literal>foo=bar baz</literal>.  Quoting the value prevents
whitespace from being used as a delimiter.</para>