diff --git a/Makefile.PL b/Makefile.PL
index aaad4c1e..8f428856 100644
--- a/Makefile.PL
+++ b/Makefile.PL
@@ -111,17 +111,26 @@ my %eumm_args = (
   ssleay(),
 );
 
+# CCFLAGS is used internally by Makefile.PL to define various C preprocessor
+# macros (as opposed to DEFINE, which is user-facing).
+$eumm_args{CCFLAGS} = $Config{ccflags};
+
+# Expose the current Perl version to the C preprocessor. This is used in
+# SSLeay.xs before perl.h is included (and therefore before its PERL_VERSION_*
+# macros are available).
+add_ccflag( $eumm_args{CCFLAGS}, "-DNET_SSLEAY_PERL_VERSION=" . $] * 1e6 );
+
 # See if integers are only 32 bits long. If they are, add a flag to
 # CCFLAGS. Since OpenSSL 1.1.0, a growing number of APIs are using 64
 # bit integers. This causes a problem if Perl is compiled without 64
-# bit integers. DEFINE is not used because Makefile.PL command line
-# DEFINE argument is used for enabling compile time PR1
-# etc. debugging.
+# bit integers.
 #
 # Note: 32bit integers are treated as the non-default case. When you
 # use this define, do it so that 64bit case is the default whenever
 # possible. This is safer for future library and Net::SSLeay releases.
-$eumm_args{CCFLAGS} = "-DNET_SSLEAY_32BIT_INT_PERL $Config{ccflags}" if !defined $Config{use64bitint} || $Config{use64bitint} ne 'define';
+if ( !defined $Config{use64bitint} || $Config{use64bitint} ne 'define' ) {
+    add_ccflag( $eumm_args{CCFLAGS}, '-DNET_SSLEAY_32BIT_INT_PERL' );
+}
 
 # This can go when EU::MM older than 6.58 are gone
 $eumm_args{AUTHOR} = join(', ', @{$eumm_args{AUTHOR}}) unless eval { ExtUtils::MakeMaker->VERSION(6.58); };
@@ -138,6 +147,12 @@ SSLeay$Config{'obj_ext'} : constants.c
 MAKE
 }
 
+# Prepends the C compiler flag in the second parameter to the string of compiler
+# flags in the first parameter.
+sub add_ccflag {
+    substr $_[0], 0, 0, $_[1] . ( length $_[0] ? ' ' : '' );
+}
+
 sub ssleay {
     my $prefix = find_openssl_prefix();
     my $exec   = find_openssl_exec($prefix);
diff --git a/SSLeay.xs b/SSLeay.xs
index 414d41da..6e7ef1d7 100644
--- a/SSLeay.xs
+++ b/SSLeay.xs
@@ -134,11 +134,13 @@
 /* Prevent warnings about strncpy from Windows compilers */
 #define _CRT_SECURE_NO_DEPRECATE
 
-/* Silence compound-token-split-by-macro warnings from perl.h when building with
- * Clang >= 12 - see GH-383
+/* Silence compound-token-split-by-macro warnings from perl.h when building for
+ * Perl < 5.35.2 with Clang >= 12 - see GH-383
  */
-#if defined(__clang__) && defined(__clang_major__) && __clang_major__ >= 12
+#if NET_SSLEAY_PERL_VERSION < 5035002 && defined(__clang__) && defined(__clang_major__) && __clang_major__ >= 12
+#pragma clang diagnostic ignored "-Wunknown-warning-option"
 #pragma clang diagnostic ignored "-Wcompound-token-split-by-macro"
+#pragma clang diagnostic warning "-Wunknown-warning-option"
 #endif
 
 #ifdef __cplusplus