The change log to Convert::UUlib 1.50 shows:
Revision history for Perl extension Convert::UUlib. 1.5 Sat Jul 11 03:56:06 CEST 2015 - fix a heap overflow (testcase by Krzysztof WojtaĆ). - on systems that support it (posix + mmap + map_anonymous), allocate all dynamic areas via mmap and put four guard pages around them, to catch similar heap overflows safely in the future. - find a safer way to pass in CC/CFLAGS to uulib. - added stability canary support. The extra protection (guard pages) is probably what is causing your crashes: previously some heap overflow could cause corruption and havoc without necessarily being noticed, bringing down a process. If I understand the changelog correctly, the new guard pages make it possible to detect some runaway memory access in uulib and terminate the process if this occurs, instead of letting a corruption spread. This is a good step in guarding against security exploits: better crash than let a leak be exploitable. Unfortunately the violation cannot be contained, which affects apparent stability. Mark