My site has a form where you can select a Stack Exchange site from a drop-down-menu. Every site has a meta, and including a "Meta X" option for every "X" in the menu (I think) is redundant. To shorten the list, there's a checkbox next to the drop-down-menu labeled "meta." Let's say you choose Stack Overflow and check "meta." Then your selection is Meta Stack Overflow.
Will this confuse users?
Yes. But maybe not very many.
An alternative would be to offer an explicit choice for Site or Meta after the initial selection. For example by showing two buttons. So one button for X, and one button for Meta X. Now the user can make two simple decisions, one after the other.
Another alternative can be to embbed a meta button into entries of our drop-down-menu. The primary action is the menu entry and the secondary is the meta version:
