$ make
 . . . stuff elided . . .
Kbh.o: In function `XS_Kbh_send_string':
/Work/Perl/Perlmonks/XS_linking/Kbh.c:173: undefined reference to `send_string'
/Work/Perl/Perlmonks/XS_linking/Kbh.c:173:(.text+0xb3): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `send_string'
collect2: error: ld returned 1 exit status
make: *** [Makefile:472: blib/arch/auto/Kbh/Kbh.dll] Error 1