imagemagick: fix perl compile

Formula/imagemagick.rb

@@ -57,6 +57,8 @@ class Imagemagick < Formula
   skip_clean :la
 
   def install
+    ENV.delete "PERL_MM_OPT"
+
     args = %W[
       --disable-osx-universal-binary
       --prefix=#{prefix}
@@ -74,7 +76,7 @@ class Imagemagick < Formula
     end
     args << "--disable-opencl" if build.without? "opencl"
     args << "--without-gslib" if build.without? "ghostscript"
-    args << "--without-perl" if build.without? "perl"
+    args << "--with-perl" << "--with-perl-options='PREFIX=#{prefix}'" if build.with? "perl"
     args << "--with-gs-font-dir=#{HOMEBREW_PREFIX}/share/ghostscript/fonts" if build.without? "ghostscript"
     args << "--without-magick-plus-plus" if build.without? "magick-plus-plus"
     args << "--enable-hdri=yes" if build.with? "hdri"
@@ -83,7 +85,7 @@ class Imagemagick < Formula
 
     if build.with? "quantum-depth-32"
       quantum_depth = 32
-    elsif build.with? "quantum-depth-16"
+    elsif build.with?("quantum-depth-16") || build.with?("perl")
       quantum_depth = 16
     elsif build.with? "quantum-depth-8"
       quantum_depth = 8
@@ -110,14 +112,8 @@ class Imagemagick < Formula
 
   def caveats
     s = <<-EOS.undent
-      For full Perl support you must install the Image::Magick module from the CPAN.
-        https://metacpan.org/module/Image::Magick
-
-      The version of the Perl module and ImageMagick itself need to be kept in sync.
-      If you upgrade one, you must upgrade the other.
-
-      For this version of ImageMagick you should install
-      version #{version} of the Image::Magick Perl module.
+      For full Perl support you may need to adjust your PERL5LIB variable:
+        export PERL5LIB="#{HOMEBREW_PREFIX}/lib/perl5/site_perl":$PERL5LIB
     EOS
     s if build.with? "perl"
   end