Try to be clearer about perlio.

p4raw-id: //depot/perl@16122

1 files changed, 11 insertions, 6 deletions

diff --git a/INSTALL b/INSTALL
index 63026ceae4..da0c726c5a 100644
--- a/INSTALL
+++ b/INSTALL
@@ -806,18 +806,23 @@ and the long double support.
 
 =head2 Selecting File IO mechanisms
 
-Previous versions of perl used the standard IO mechanisms as defined in
-stdio.h.  Versions 5.003_02 and later of perl allowed alternate IO
-mechanisms via a "PerlIO" abstraction, but the stdio mechanism is still
-the default and is the only supported mechanism.
+Executive summary: in Perl 5.8 you should use the default "PerlIO"
+as the IO mechanism unless you have a good reason not to.
+
+In more detail: previous versions of perl used the standard IO
+mechanisms as defined in stdio.h.  Versions 5.003_02 and later of perl
+introuced alternate IO mechanisms via a "PerlIO" abstraction, but up
+until and including Perl 5.6 stdio mechanism was still the default and
+the only supported mechanism.
 
 Starting from Perl 5.8 the default mechanism is to use the PerlIO
 abstraction, because it allows better control of I/O mechanisms,
 instead of having to work with (often, work around) vendors' I/O
 implementations.
 
-This PerlIO abstraction can be disabled either on the Configure
-command line with
+This PerlIO abstraction can be disabled (but again, unless you know
+what you are doing, should not) either on the Configure command line
+with
 
 	sh Configure -Uuseperlio