-The optional QUALIFIER subcommand names a character that can be used
-to quote values within fields in the input. A field that begins with
-the specified quote character ends at the next match quote.
-Intervening delimiters become part of the field, instead of
-terminating it.
+The optional QUALIFIER subcommand names one or more characters that
+can be used to quote values within fields in the input. A field that
+begins with one of the specified quote characters ends at the next
+matching quote. Intervening delimiters become part of the field,
+instead of terminating it. The ability to specify more than one quote
+character is a PSPP extension.
+
+By default, a character specified on QUALIFIER cannot itself be
+embedded within a field that it quotes, because the quote character
+always terminates the quoted field. With ESCAPE, however, a doubled
+quote character within a quoted field inserts a single instance of the
+quote into the field. For example, if @samp{'} is specified on
+QUALIFIER, then without ESCAPE @code{'a''b'} specifies a pair of
+fields that contain @samp{a} and @samp{b}, but with ESCAPE it
+specifies a single field that contains @samp{a'b}. ESCAPE is a PSPP
+extension.