What would really help here is to have debugging symbols on your libc.so and libperl.so, so you could do an "l" and see what exact code was being run in those crashing functions, with what values. On Debian derivatives that should be achievable by installing the appropriate packages.

A quick surmise from the first stack-trace is that Net::Curl appears to be pthreading to do its thing, then calling a Perl callback. Perl in this context may or may not be thread-safe, which would explain crashes. You haven't published an SSCCE so we can't really tell more than that. You should update to include one.