Rollback untoward mutations.

lib/pry/cli.rb

@@ -114,7 +114,7 @@ Copyright (c) 2013 John Mair (banisterfiend)
 --
 }
   on :e, :exec=, "A line of code to execute in context before the session starts" do |input|
-    exec_string << input << "\n"
+    exec_string + input + "\n"
   end
 
   on "no-pager", "Disable pager for long output" do

lib/pry/commands/amend_line.rb

@@ -52,7 +52,7 @@ class Pry
     end
 
     def replace_in_array(array, range)
-      array[range] = arg_string << "\n"
+      array[range] = arg_string + "\n"
     end
 
     # @return [Fixnum] The number of lines currently in `eval_string` (the input buffer).

lib/pry/commands/find_method.rb

@@ -97,7 +97,7 @@ class Pry
       output.puts text.bold(klass.name)
       grouped[klass].each do |method|
         header = method.name_with_owner
-        output.puts header << additional_info(header, method)
+        output.puts header + additional_info(header, method)
       end
     end
 

lib/pry/indent.rb

@@ -156,7 +156,7 @@ class Pry
         before.times{ prefix.sub! SPACES, '' }
         new_prefix = prefix + SPACES * after
 
-        line = prefix << line.lstrip unless previously_in_string
+        line = prefix + line.lstrip unless previously_in_string
 
         output += line