Add Return The Thing Being Printed as a Ruby TIL

ruby/return-the-thing-being-printed.md

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+# Return The Thing Being Printed
+
+The [`puts`](https://ruby-doc.org/core-3.0.2/Kernel.html#method-i-puts) method
+is the canonical way of priting things to stdout in Ruby. Notably, its return
+value is always `nil`. Generally this isn't much of an issue, but can be a
+potential gotcha while debugging.
+
+Consider the following method whose behavior you are trying to investigate:
+
+```ruby
+def process(arg)
+  thing = do_something(arg)
+
+  thing.value
+end
+```
+
+I want to print out the value of thing when I execute the code to see what it
+is while debugging. So I add a `puts` statement.
+
+```ruby
+def process(arg)
+  thing = do_something(arg)
+
+  puts thing.value
+end
+```
+
+Well, I just broke the behavior of `process` because it now returns `nil`
+instead of `thing.value`.
+
+I could add an additional line that returns the correct value. Or I could use
+[`p`](https://ruby-doc.org/core-3.0.2/Kernel.html#method-i-p) which both prints
+its argument to stdout and returns it as is.
+
+```ruby
+def process(arg)
+  thing = do_something(arg)
+
+  p thing.value
+end
+```
+
+[source](https://dev.to/lofiandcode/ruby-puts-vs-print-vs-p-vs-pp-vs-awesome-5akl)