Make plperl's $_TD trigger data a global rather than a lexical variable,
with a fresh local value for each invocation, to avoid unexpected sharing
violations. Per recent -hackers discussion.

doc/src/sgml/plperl.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.53 2006/05/26 17:34:16 adunstan Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/plperl.sgml,v 2.54 2006/05/29 13:51:23 adunstan Exp $ -->
 
  <chapter id="plperl">
   <title>PL/Perl - Perl Procedural Language</title>
@@ -660,8 +660,9 @@ $$ LANGUAGE plperl;
   <para>
    PL/Perl can be used to write trigger functions.  In a trigger function,
    the hash reference <varname>$_TD</varname> contains information about the
-   current trigger event.  The fields of the <varname>$_TD</varname> hash
-   reference are:
+   current trigger event. <varname>$_TD</> is a global variable, 
+   which gets a separate local value for each invocation of the trigger. 
+   The fields of the <varname>$_TD</varname> hash reference are:
 
    <variablelist>
     <varlistentry>

src/pl/plperl/plperl.c

 /**********************************************************************
  * plperl.c - perl as a procedural language for PostgreSQL
  *
- *	  $PostgreSQL: pgsql/src/pl/plperl/plperl.c,v 1.109 2006/05/26 17:34:16 adunstan Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plperl/plperl.c,v 1.110 2006/05/29 13:51:23 adunstan Exp $
  *
  **********************************************************************/
 
@@ -771,7 +771,7 @@ plperl_create_sub(char *s, bool trusted)
 	ENTER;
 	SAVETMPS;
 	PUSHMARK(SP);
-	XPUSHs(sv_2mortal(newSVpv("my $_TD=$_[0]; shift;", 0)));
+	XPUSHs(sv_2mortal(newSVpv("our $_TD; local $_TD=$_[0]; shift;", 0)));
 	XPUSHs(sv_2mortal(newSVpv(s, 0)));
 	PUTBACK;