Шаблон:exists/doc

If there is a page with the same name as the argument to page=, this template prints the argument to then=. Otherwise, it prints the argument to else=

For example,

{{exists|page=a|then=a|else=b}}

prints '''a''', since that page exists. But,

{{exists|page=hwgjvecfdtygwekfhn|then=hello|else=world}}

prints '''world''', since the page with the garbage name does not exist.