Sort of success.

I finally got a build/test/install to work by using the portable code

$ perl Makefile.PL machine=port
[download]

Obviously this is not ideal. If I follow the manual instructions then I get (note this is different from the initial problem as that used pari 2.2)

First I need to edit the code that FTP's pari libs as I can't use exte
+rnal ftp.  All I did was point at localhost and put the archive in a 
+known place.

$ perl Makefile.PL
...
gets the code (2.1.7) and patches it.
id's my machine as sparcv9 so sets build to sparcv8-micro
...
$ make
...
(compiling gen1.c)
./pariinl.h: In function `gmul':
./pariinl.h:887: error: asm-specifier for variable `hiremainder' confl
+icts with asm clobber list
...
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Now if I try to config and build libpari separately.

$ make gp
...
(compiling mp.c)
../src/kernel/none/mp.c: In function `addrr':
../src/kernel/none/mp.c:598: error: asm-specifier for variable `overfl
+ow' conflicts with asm clobber list
../src/kernel/none/mp.c:634: confused by earlier errors, bailing out
...
[download]

I get the same errors if I manually get pari, unpack it to a sibling of the Math::Pari build area, Configure libpari then try to make Math::Pari.