The way I'm slowly understanding it is, all languages have a use. All of them. Look at fortran, basic, perl, c, etc etc.. Some, you have no choice to use, like ASM, so let's skip that one. Anyway, you have all of these languages, and a new one pops up. It gets used for one thing or another. It's novel. People like the syntax and the usage and it gains some traction. Then it loses its luster. That isn't it though.

The language has most likely, filled a few niches. The C language is THE thing you write your OS in once you can write a C compiler for your OS, or can cross compile from another OS. BASIC and COBOL found niches of their own, such as being implemented in every damned place, or as a business language. A niche does not mean that it cannot spill over into other realms, and stay usable. I.e. using C to what PHP excels at.

I believe Perl gained popularity in text processing and the likes as sed and awk are not, something. Elegant? Easy? Just not something. CGI is just that though, text processing, and that's where things got really easy for Perl in gaining a niche. At least until "better" ways came about. Some will argue php to gained traction as being easier than Perl over CGI. PHP did something that perl couldn't at that time, which is to become novel.

Where does Perl fit in? It makes easy things brain dead easy, and hard things possible for a lot of things, nothing uberly-specific. Will it die? As long as there's a need for a jack-of-all trades, master of none, yes, perl can do this and more. It's as if Perl became the new shell programming. You can string enough tools, in the form of CPAN modules together, and you can do some things with so little effort, it's criminal.

Will php live on in a niche, like c is for system programming, perl as a do-it-all language, and what not? Maybe RoR will kill it off? Who knows?

One could argue java is a better business language, but so was cobol at one point. It seems that well written languages seem to last longest because they fit their niches well by design. I'd argue Perl5, while ugly at times, is well written. It will last for some time longer as C and Fortran has in their niches. But watch out, when Perl6 comes out, everyone will go ga-ga, and the cycle occurs. *again*