Not all programming languages endure forever. In fact, even the most popular ones inevitably crumble away, as new generations of developers embrace other languages and frameworks they find easier to work with.

In order to determine which programming languages are likely doomed in the medium- to long-term, we looked at the popularity rankings by TIOBE and RedMonk, as well as Dice’s own database of job postings. If your career is based on any of the following languages, we suggest diversifying your skill-set at some point.

Ruby

Once upon a time, Ruby enjoyed a fair bit of popularity. It was a top-ten language on TIOBE’s monthly list, and developers praised how easy it was to learn. But over the past 18 months, it has dipped in TIOBE’s rankings, from ninth to 12th place (after falling at one point to 16th).

Even more disturbing: An analysis of Dice job-posting data over the past year shows a startling dip in the number of companies looking for technology professionals who are skilled in Ruby. In 2018, the number of Ruby jobs declined 56 percent. That’s a huge warning sign that companies are turning away from Ruby—and if that’s the case, the language’s user-base could rapidly erode to almost nothing.

(That being said, it’s taking awhile for Ruby to finally give up the ghost; we’ve been monitoring its descent for quite some time, even as coding bootcamps and developers have given it up.)

Haskell

Supposedly, Haskell is headed for a major standard update in 2020 (check out GHC, as well as GitHub’s Haskell-related repos). A number of prominent firms and projects (Facebook, GitHub, etc.) have all used Haskell to implement vital programs at one point or another. However, Haskell continues to flatline on RedMonk’s long-term language rankings, suggesting that there’s virtually no developer buzz around it. Dying, or totally dead?

Objective-C

Apple’s Objective-C is 35 years old, and it’s clear that the company wants it dead. Five years ago, Apple executives took to the stage to unveil Swift, its new-and-improved programming language for its software ecosystem. No doubt they expected developers to quickly embrace Swift at Objective-C’s expense.

And to be fair, more developers have begun using Swift (especially as it’s become more feature-rich), but Objective-C hasn’t crashed as much in the popular-language rankings as some folks might have expected. Blame that on 35 years of legacy code, and many developers simply preferring to work with a language they’ve always used.

At some point, though, Objective-C will likely fade away entirely. Apple’s too keen on its eventual demise, and Swift is becoming an incredibly effective language for building iOS, macOS, and, soon, cross-platform apps.

R

Back in the day, R was an increasingly popular language for data analytics. However, it seems that Python is rapidly swallowing up R’s market-share. Although R is still used by academics and data scientists, companies interested in data analytics are turning to Python for its scalability and ease of use. As a result, R has dipped on TIOBE’s index of programming language popularity, and other studieshave shown a slow decline in R usage in favor of Python.

If R is going to survive in any form, it’s because data analysts might end up using it in conjunction with Python. “Combining R and Python is both reasonable and feasible,” Enriko Aryanto, the CTO and a co-founder of the Redwood City, Calif.-based QuanticMind, a data platform for intelligent marketing, told Dice earlier this year. “We run them both in our data science platform internally. But if I were starting my career all over again today, I might consider focusing on Python rather than R. It’s a more-general language with broader applications.”

But even that scenario might end with R used by a handful of academics and nobody else. That’s not viable.

Perl

Even if RedMonk has Perl’s popularity declining, it’s still going to take a long time for the language to flatten out completely, given the sheer number of legacy websites that still feature its code. Nonetheless, widespread developer embrace of other languages for things like building websites, means that Perl is going to just fall into increasing disuse.

Meanwhile, if you ever wondered about which languages are (probably) slated for continuing uptake and possible greatness, we have a list for that, too.

(Note: In an earlier version of this article, we said that Perl had little to no active development. As some helpful commenters pointed out, that’s actually not the case: it’s updated annually. However, given its decline on RedMonk and TIOBE, we still argue that this is a declining language.)