I could not find any useful documentation on the Perl compile time operators.

A lot of that is in INSTALL. The rest you'll have to grep the source code for; the pod/perl*delta.pod files also often contain useful information.

PERL_HASH_FUNC_ONE_AT_A_TIME_HARD

That's one of the hash functions (at least according to perl5180delta, I can't find many references in the source itself), and you can see some more options if you search for "PERL_HASH_FUNC" in INSTALL. However, unless you have a specific reason to change this from the default, I'd recommend sticking with the default.

PERL_SAWAMPERSAND

I believe this has to do with the performance issues that $& suffered from before Perl 5.20. According to perl5200delta, "The previous behaviour can still be enabled by running Configure with -Accflags=-DPERL_SAWAMPERSAND." So again, unless you have a very specific reason for enabling this, I'd suggest just leaving it at the default.