1 files changed, 76 insertions, 0 deletions
diff --git a/contrib/perl5/lib/open.pm b/contrib/perl5/lib/open.pm
new file mode 100644
index 000000000000..cdd20ac2c392
--- /dev/null
+++ b/contrib/perl5/lib/open.pm
@@ -0,0 +1,76 @@
+package open;
+$open::hint_bits = 0x20000;
+
+sub import {
+    shift;
+    die "`use open' needs explicit list of disciplines" unless @_;
+    $^H |= $open::hint_bits;
+    while (@_) {
+	my $type = shift;
+	if ($type =~ /^(IN|OUT)\z/s) {
+	    my $discp = shift;
+	    unless ($discp =~ /^\s*:(raw|crlf)\s*\z/s) {
+		die "Unknown discipline '$discp'";
+	    }
+	    $^H{"open_$type"} = $discp;
+	}
+	else {
+	    die "Unknown discipline class '$type'";
+	}
+    }
+}
+
+1;
+__END__
+
+=head1 NAME
+
+open - perl pragma to set default disciplines for input and output
+
+=head1 SYNOPSIS
+
+    use open IN => ":crlf", OUT => ":raw";
+
+=head1 DESCRIPTION
+
+The open pragma is used to declare one or more default disciplines for
+I/O operations.  Any open() and readpipe() (aka qx//) operators found
+within the lexical scope of this pragma will use the declared defaults.
+Neither open() with an explicit set of disciplines, nor sysopen() are
+influenced by this pragma.
+
+Only the two pseudo-disciplines ":raw" and ":crlf" are currently
+available.
+
+The ":raw" discipline corresponds to "binary mode" and the ":crlf"
+discipline corresponds to "text mode" on platforms that distinguish
+between the two modes when opening files (which is many DOS-like
+platforms, including Windows).  These two disciplines are currently
+no-ops on platforms where binmode() is a no-op, but will be
+supported everywhere in future.
+
+=head1 UNIMPLEMENTED FUNCTIONALITY
+
+Full-fledged support for I/O disciplines is currently unimplemented.
+When they are eventually supported, this pragma will serve as one of
+the interfaces to declare default disciplines for all I/O.
+
+In future, any default disciplines declared by this pragma will be
+available by the special discipline name ":DEFAULT", and could be used
+within handle constructors that allow disciplines to be specified.
+This would make it possible to stack new disciplines over the default
+ones.
+
+    open FH, "<:para :DEFAULT", $file or die "can't open $file: $!";
+
+Socket and directory handles will also support disciplines in
+future.
+
+Full support for I/O disciplines will enable all of the supported
+disciplines to work on all platforms.
+
+=head1 SEE ALSO
+
+L<perlfunc/"binmode">, L<perlfunc/"open">, L<perlunicode>
+
+=cut