core file --- a file written by the kernel when it is terminating a process as a result of the default action of certain singals. Which signals varies from system to system. A typical list might be SIGABRT, SIGFPE, SIGILL, SIGQUIT, SIGSEGV, and SIGBUS.
With most versions of UNIX, yes they start out with a name of core. But some versions of UNIX give you control over the name. Recent SunOS versions have a coreadm command that can do this.
And you can always do something like "mv core perl.core".
I certainly would not assume that a file with "core" somewhere in the name must be a core file. To be sure, you need to inspect the contents somehow. In previous posts people have described tools like: "file", and "adb". Did you find any that work on your system? Try it against these candidates.
But bear in mind that if someone did do "mv core perl.core", it may that they want that file.