This is merely a bug in t/11_pc_expo.t.
This patch (which is also needed for -Dusequadmath builds of perl) should take care of it:

--- t/11_pc_expo.t_orig	2011-08-17 22:10:34.000000000 +1000
+++ t/11_pc_expo.t	2024-09-22 11:58:20.591603700 +1000
@@ -32,5 +32,5 @@
 $obj = $pc->decode($js);
 is($obj->[0], 1.01e+30, 'digit 1.01e+30');
 $js = $pc->encode($obj);
-like($js,qr/\[1.01[Ee]\+0?30\]/, 'digit 1.01e+30');
+like($js,qr/\[1.01[Ee]\+0?30|1010000000000000000000000000000\]/, 'digit 1.01e+30');