Real is often used in place of really, most often in conversational English.

Example 1 (incorrect usage): I am real tired today.

Example 2 (correct usage): I am really tired today.

Although this error is somewhat acceptable in informal conversation, it is actually incorrect and should never be used in writing. The reason that real is incorrect when used this way is simple: Real is an adjective, and as you can see in the first example above, real is incorrectly used as an adverb. In the example, real is describing tired, which is an adjective, so the adverb really is needed to make the sentence correct.