They are different @SerendipityJane .
But those who do want to use religion as to push for political control will use religion, because it is a rather convenient way.
It took many centuries and the spilled blood and ashes (Christianity did burn people alive at some point in history!) of our ancestors in Europe, but we got there, amidst not perfect separation, but a doable one. Not perfect, but it allows us freedom. And I think it is a good base for mixed communities indeed. If you live in UK today, you do not need to ever hear a single word from a religious book if you are not inclined to do so.
If the rule of the land includes freedom of religious belief and practice, equality for women (including the right to work to support their families), an elected political representation, freedom of speech, rights to education, health care and so on, there is a political and law system separated from religion.
If the rules of the land start by impossing a single religion and worship practice (though they may tollerate a list of others), continue with listing what women ( or other individuals, but women seem to be the primary target) can wear, do and say, and they profess to follow a particular religion, then you have a political regime using the excuse of religion. They will kill people who do not comply (against chore principle of most religions), force people into practices (again, most religions are meant to take natural place in the heart of the believer, not forced)...
So, secular systems will mention freedom and religionS. Yes, they will be influenced by culture, which is influenced by religion and they will not be perfect, I know. But extremist regimes will proclaim a single religion, while violating its values, one after another. It is only the extreme ones who deny a difference between religion and policy/ politics.