irb(main):001:0> ['foo', 'foo bar', 'foo 007', 'foo007', '007'].map { |s| s.tr('^A-Za-z0-9', '') }
=> ["foo", "foobar", "foo007", "foo007", "007"]

irb(main):002:0> ['foo', 'foo bar', 'foo 007', 'foo007', '007'].map { |s| s.tr!('^A-Za-z0-9', '') }
=> [nil, "foobar", "foo007", nil, nil]