Use block variable instead of global

```ruby
require 'benchmark/ips'

Benchmark.ips do |x|
  x.report("$&") {
    "foo".sub(/f/) { $&.upcase }
  }
  x.report("block var") {
    "foo".sub(/f/) {|match| match.upcase }
  }
end

```

```
Calculating -------------------------------------
                  $&    48.658k i/100ms
           block var    49.666k i/100ms
-------------------------------------------------
                  $&    873.156k (± 9.3%) i/s -      4.331M
           block var    969.744k (± 9.2%) i/s -      4.818M
```

It's faster, and gets rid of a few "magic" global variables

1 files changed, 2 insertions, 2 deletions

diff --git a/activesupport/lib/active_support/inflector/methods.rb b/activesupport/lib/active_support/inflector/methods.rb
index bde70d772d..49fd1723e2 100644
--- a/activesupport/lib/active_support/inflector/methods.rb
+++ b/activesupport/lib/active_support/inflector/methods.rb
@@ -68,9 +68,9 @@ module ActiveSupport
     def camelize(term, uppercase_first_letter = true)
       string = term.to_s
       if uppercase_first_letter
-        string = string.sub(/^[a-z\d]*/) { inflections.acronyms[$&] || $&.capitalize }
+        string = string.sub(/^[a-z\d]*/) { |match| inflections.acronyms[match] || match.capitalize }
       else
-        string = string.sub(/^(?:#{inflections.acronym_regex}(?=\b|[A-Z_])|\w)/) { $&.downcase }
+        string = string.sub(/^(?:#{inflections.acronym_regex}(?=\b|[A-Z_])|\w)/) { |match| match.downcase }
       end
       string.gsub!(/(?:_|(\/))([a-z\d]*)/i) { "#{$1}#{inflections.acronyms[$2] || $2.capitalize}" }
       string.gsub!('/'.freeze, '::'.freeze)