The problem can be summarized as follows:
- Some platforms ship with a vendor-supplied libc that's really sloppy.
- Because of this, perl5 development has been slowly replacing use of libc with home-grown code.
- However, GNU libc is really good. It's the default libc on many platforms, and it's available on most.
- As a result, many perl programmers have been experiencing slowly deteriorating quality of numeric implementation for around two decades. Perl6 accelerates this trend.