Coming of age sexually as a 21st century girl is an excruciating task.

Girls today face a confusing mix of sex and love, exacerbated by the prevalence of hookup culture, the complexities of dating apps, and a society that is becoming more and more saturated with pornography.

That’s where Louise Perry would like to step in and offer some help. In her book “A New Guide to Sex in the 21st Century” Perry speaks directly to 15- to 17-year-old girls about why she believes progressive feminism is shortchanging them.

“The main thing that I took away from the writing process is how poorly we’ve served young people as a culture,” Perry told The Post.

She hopes her book will help young women today avoid making the mistakes of their millennial predecessors, many of whom now regret spending their 20s dating casually and sleeping around.

“I’m not preaching abstinence per se,” Perry explained. “I’m actually saying, honestly, you’ll be happier in retrospect to just skip that whole part of the progressive life narrative.

“It’s not a compulsory adventure you have to go through in your twenties. You could simply not, and actually you would live a happier life for it.”

The book, out March 10, is a teenaged adaptation of Perry’s previous book “The Case Against The Sexual Revolution,” per popular demand from parents desperate to get her message through to their daughters. 

“[Young women] have been denied the guidance of mothers, not because their actual mothers are unwilling to offer it, but modern feminism has encouraged them not to listen [to them],” she writes.

Certain cultural references are tailored for the age group, for instance Perry explains who sex icons Marilyn Monroe and Hugh Hefner are to a teen audience who might not actually know.

The language in this updated version is also simplified and some graphic details about sex have been toned down. 

But it still comes with a heavy dose of reality checks, such as: “While the 1950s ‘angel of the house’ hid her apron, the modern ‘angel of the bedroom’ hides her pubic hair.

“She pretends to orgasm, pretends to like anal sex, and pretends not to mind when the ‘friends with benefits’ arrangement causes her pain.”

Perry’s book is a brutally honest evisceration of a hookup culture that leaves young men feeling gratified and young women feeling used.

“I speak to young women, and the only sex they’ve ever had has been casual sex,” she told The Post.

“They never actually had a proper boyfriend. That was unheard of a couple of decades ago, but now it seems to be quite widespread.”

Perry argues in her book that hookup culture has coerced women into an unsatisfying predicament: “The evidence doesn’t reveal a generation of women reveling in sexual liberation — instead, a lot of women seem to be having unpleasant, crappy sex out of a sense of obligation.”

Her advice: “Only have sex with a man if you think he would make a good father to your children. This isn’t because you necessarily intend to have children with him, but because this is a good rule of thumb in deciding whether or not he’s worthy of your trust.”

Perry argues that, although she is in favor of birth control, it had the cultural side effect of removing the stakes from sex: “The pill offers this illusion of sex being a meaningless leisure activity. But just because you’re taking a contraceptive pill does not mean that you’re not emotionally affected by sex.”

While her message is certainly socially conservative, Perry points out that her book is entirely secular and non-partisan in its reasoning.

“I wrote the original book very much intending it to be read by myself aged about 20, when I was progressive, and I would not have been receptive to a conservative or a religious argument,” she explained. “It’s intended to persuade people who are not with the program.”

She’s hoping to reach progressive teenagers, who are likely to buy progressive feminist rhetoric hook, line, and sinker: “Teenagers just lap up this ideological stuff without even realizing that’s what it is.”

The most important message she hopes readers walk away with is that “sex positive feminism” is “basically cope.”

“Women want to tell themselves that getting ghosted by this Tinder date was actually good for me,” she said. “They’re soothing feelings of distress generated by a sexual culture, which actually isn’t good for women.”

Perry is right that a generation of young women are growing up knowing nothing other than a hookup culture that sees the majority of college girls getting choked in bed, rather than finding fulfilling relationships they desire.

More and more young girls are waking up to the idea something is wrong with our sexual culture, but they’re getting seduced by the wrong messaging — falling down the rabbitholes of regressive, reactionary trends like trad-wives and stay-at-home-girlfriends.

Girls are in need of an honest voice of reason who tells it to them like it is, and empowers them to demand respect for themselves and their bodies in an age of sexual anarchy. With “A New Guide to Sex in the 21st Century,” Perry seems poised to do just that.