diff -r -u parrot-current/config/auto/format.pm parrot-andy/config/auto/format.pm
--- parrot-current/config/auto/format.pm	2009-02-01 20:44:28.000000000 -0500
+++ parrot-andy/config/auto/format.pm	2009-02-09 09:08:59.000000000 -0500
@@ -15,6 +15,7 @@
 
 use strict;
 use warnings;
+use Config;  # for long double printf format
 
 use base qw(Parrot::Configure::Step);
 
@@ -115,7 +116,13 @@
         # Stay way from long double for now (it may be 64 or 80 bits)
         # die "long double not supported at this time, use double.";
         $nvsize   = $ldsize;
-        $nvformat = "%Lf";
+        if (defined($Config{'sPRIgldbl'})) {
+            $nvformat = "%.15" .  $Config{'sPRIgldbl'};
+            $nvformat =~ s/"//g;   # Perl 5's Config value has embedded double quotes
+        }
+        else {
+            die qq{Configure.pl:  Can't find a printf-style format specifier for type '$nv'\n};
+        }
     }
     else {
         die qq{Configure.pl:  Can't find a printf-style format specifier for type '$nv'\n};