"92. Exclusion of evidence of oral agreement.—When the terms of any such contract, grant or other disposition of property, or any matter required by law to be reduced to the form of a document, have been proved according to the last section, no evidence of any oral agreement or statement shall be admitted, as between the parties to any such instrument or their representatives in interest, for the purpose of contradicting, varying, adding to, or subtracting from, its terms: Proviso (1) .—Any fact may be proved which would invalidate any document, or which would entitle any person to any decree or order relating thereto; such as fraud, intimidation, illegality, want of due execution, want of capacity in any contracting party, 1[want or failure] of consideration, or mistake in fact or law Proviso (2).—The existence of any separate oral agreement as to any matter on which a document is silent, and which is not inconsistent with its terms, may be proved. In considering whether or not this proviso applies, the Court shall have regard to the degree of formality of the document: "