Concatenates each object in +objects+ to +self+; returns +self+:

  'foo'.concat('bar', 'baz') # => "foobarbaz"

For each given object +object+ that is an integer,
the value is considered a codepoint and converted to a character before concatenation:

  'foo'.concat(32, 'bar', 32, 'baz') # => "foo bar baz" # Embeds spaces.
  'こん'.concat(12395, 12385, 12399)  # => "こんにちは"

Related: see {Converting to New String}[rdoc-ref:String@Converting+to+New+String].
