Indeed, Borland compilers are supported but nowadays this support is much smaller than earlier.

Also, Borland build uses win32/makefile.mk and not win32/Makefile . It is quite often someone adds modification in perl5porters list to win32/Makefile and forgets to update appropriately win32/makefile.mk, or even does not know about such file.

There is a probability that you get failings that could be fixed by editing win32/makefile.mk

About couple of years ago I've discovered failed test that was caused by a bug in Borland C's CRT, and tried to report that bug to Borland with no success.

BTW do you try building with pure Borland-C-5.5, or you have such a compiler with C++Builder with VCL library?

Also, what special benefits do you want to gain by building with Borland compiler?
I can assure you that it's harder to build other modules with Borland than with MSVC++, namely because nowadays it is less supported.

Courage, the Cowardly Dog