Sun's implementation of "test" doesn't understand "==", equality of strings needs to be tested by "=". Otherwise the Singular/configure script fails with
checking whether compiler accepts -pipe... (cached) yes
checking whether _AIX is defined... (cached) no
checking whether make sets ${MAKE}... (cached) yes
configure: warning: building without lex -- make might fail
checking for bison... (cached) where-is-your-bison
checking whether ln -s works... (cached) yes
checking for perl5... (cached) perl
./configure: test: unknown operator ==
configure: error: ./configure failed for Singular
Unable to configure Singular.
I'll attach a patch for Singular/
configure.in. Unfortunately my autoconf seems to be too incompatible, so I can't make the configure script. But I manually changed == to = in configure and it worked, so I'm fairly confident that the patch to the autoconf sources is correct.