language/perl: add detected_perl_shebang

Library/Homebrew/language/perl.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+module Language
+  module Perl
+    module Shebang
+      module_function
+
+      def detected_perl_shebang(formula = self)
+        perl_path = if formula.uses_from_macos_elements&.include? "perl"
+          "/usr/bin/perl"
+        elsif formula.deps.map(&:name).include? "perl"
+          Formula["perl"].opt_bin/"perl"
+        else
+          raise "Cannot detect Perl shebang: formula does not depend on Perl."
+        end
+
+        Utils::Shebang::RewriteInfo.new(
+          %r{^#! ?/usr/bin/(env )?perl$},
+          20, # the length of "#! /usr/bin/env perl"
+          perl_path,
+        )
+      end
+    end
+  end
+end