if actually true, then
This expression has a meaning of "if the statement (in the preceding clause) is actually true, then…" It is generally only used in casual conversation.
This expression only sounds natural when the following clause contains an imperative, propositive, or a form which expresses the speaker's will or conjecture, such as -겠-, -(으)ㄹ 것이다, or -(으)려고 하다.
The meaning of the -거든 form which occurs mid-sentence is very different from the -거든 form which occurs in the sentence-final position.
Express that if the preceding statement turns out to be true, then the following statement can happen.
거든(요) (Conditional) usually appear in the middle of the sentence while 거든(요) (Reasoning) can have 요 at the end of the sentence and is used at the end of the sentence.