If you use OSR 5.0.5 cc/Robert Lipes old gcc or Egcs 1.0.X and gcc 2.95
you may need to edit the Makefile in top and each subdirectory.
SCO cc or OLD gcc                    New (Note it defaults to -melf)
CC = cc -belf (gcc -belf -fpic)      gcc
CCCDLFLAGS = -KPIC -W1,-Bexport      CCCDLFLAGS = -fpic
CCDLFAGS = -wl,-Bexport              CCDLFLAG =
LD = ld (gcc -belf -G -fpic)         LD = gcc -G -fpic
LDFLAGS = -L/usr/local/lib           LDFLAGS = -L/usr/local/lib
LD = ld (gcc -belf -G -fpic)         LD = gcc -G -fpic
OPTIMISE = Od                        OTIMISE = O1

OLD
CCCFLAGS = -belf -dy -w0 -U M_XENIX -DPERL_SCO5 -I/usr/local/include

NEW
CCCFLAGS = -U M_XENIX -DPERL_SCO5 -I/usr/local/include