Hello Howard,
I did check compilation steps following your advice and I found the library "libperl.so" was not in the compliation argument of libbackends.a. After a few tries how to provide it (way of & format), I found it was enough to set following variable as : LDFLAGS=/usr/lib64/libperl.so before to do the "configure".
By doing this, I was able to compile 2.5.7 version with back-perl module enabled :-)
Thx for help.
Brgds, Jean-Luc.