+# When building a "variant" shared library, with a custom SONAME, also customize
+# all the symbol versions. This produces a shared object that can coexist
+# without conflict in the same address space as a default build, or an object
+# with a different variant tag.
+#
+# For example, with a target definition that includes:
+#
+# shlib_variant => "-opt",
+#
+# we build the following objects:
+#
+# $ perl -le '
+# for (@ARGV) {
+# if ($l = readlink) {
+# printf "%s -> %s\n", $_, $l
+# } else {
+# print
+# }
+# }' *.so*
+# libcrypto-opt.so.1.1
+# libcrypto.so -> libcrypto-opt.so.1.1
+# libssl-opt.so.1.1
+# libssl.so -> libssl-opt.so.1.1
+#
+# whose SONAMEs and dependencies are:
+#
+# $ for l in *.so; do
+# echo $l
+# readelf -d $l | egrep 'SONAME|NEEDED.*(ssl|crypto)'
+# done
+# libcrypto.so
+# 0x000000000000000e (SONAME) Library soname: [libcrypto-opt.so.1.1]
+# libssl.so
+# 0x0000000000000001 (NEEDED) Shared library: [libcrypto-opt.so.1.1]
+# 0x000000000000000e (SONAME) Library soname: [libssl-opt.so.1.1]
+#
+# We case-fold the variant tag to upper case and replace all non-alnum
+# characters with "_". This yields the following symbol versions:
+#
+# $ nm libcrypto.so | grep -w A
+# 0000000000000000 A OPENSSL_OPT_1_1_0
+# 0000000000000000 A OPENSSL_OPT_1_1_0a
+# 0000000000000000 A OPENSSL_OPT_1_1_0c
+# 0000000000000000 A OPENSSL_OPT_1_1_0d
+# 0000000000000000 A OPENSSL_OPT_1_1_0f
+# 0000000000000000 A OPENSSL_OPT_1_1_0g
+# $ nm libssl.so | grep -w A
+# 0000000000000000 A OPENSSL_OPT_1_1_0
+# 0000000000000000 A OPENSSL_OPT_1_1_0d
+#
+(my $SO_VARIANT = qq{\U$target{"shlib_variant"}}) =~ s/\W/_/g;
+