1 files changed, 77 insertions, 0 deletions
diff --git a/contrib/perl5/lib/base.pm b/contrib/perl5/lib/base.pm
new file mode 100644
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+++ b/contrib/perl5/lib/base.pm
@@ -0,0 +1,77 @@
+=head1 NAME
+
+base - Establish IS-A relationship with base class at compile time
+
+=head1 SYNOPSIS
+
+    package Baz;
+    use base qw(Foo Bar);
+
+=head1 DESCRIPTION
+
+Roughly similar in effect to
+
+    BEGIN {
+	require Foo;
+	require Bar;
+	push @ISA, qw(Foo Bar);
+    }
+
+Will also initialize the %FIELDS hash if one of the base classes has
+it.  Multiple inheritance of %FIELDS is not supported.  The 'base'
+pragma will croak if multiple base classes has a %FIELDS hash.  See
+L<fields> for a description of this feature.
+
+When strict 'vars' is in scope I<base> also let you assign to @ISA
+without having to declare @ISA with the 'vars' pragma first.
+
+This module was introduced with Perl 5.004_04.
+
+=head1 SEE ALSO
+
+L<fields>
+
+=cut
+
+package base;
+
+sub import {
+    my $class = shift;
+    my $fields_base;
+
+    foreach my $base (@_) {
+	unless (defined %{"$base\::"}) {
+	    eval "require $base";
+	    # Only ignore "Can't locate" errors from our eval require.
+	    # Other fatal errors (syntax etc) must be reported.
+	    die if $@ && $@ !~ /^Can't locate .*? at \(eval /;
+	    unless (defined %{"$base\::"}) {
+		require Carp;
+		Carp::croak("Base class package \"$base\" is empty.\n",
+			    "\t(Perhaps you need to 'use' the module ",
+			    "which defines that package first.)");
+	    }
+	}
+
+	# A simple test like (defined %{"$base\::FIELDS"}) will
+	# sometimes produce typo warnings because it would create
+	# the hash if it was not present before.
+	my $fglob;
+	if ($fglob = ${"$base\::"}{"FIELDS"} and *$fglob{HASH}) {
+	    if ($fields_base) {
+		require Carp;
+		Carp::croak("Can't multiply inherit %FIELDS");
+	    } else {
+		$fields_base = $base;
+	    }
+	}
+    }
+    my $pkg = caller(0);
+    push @{"$pkg\::ISA"}, @_;
+    if ($fields_base) {
+	require fields;
+	fields::inherit($pkg, $fields_base);
+    }
+}
+
+1;