I pasted the output below for your reference.

C:\Perl>cpan DBD::Sybase
Set up gcc environment - 3.4.5 (mingw-vista special r3)
CPAN: Term::ANSIColor loaded ok (v4.02)
CPAN: Storable loaded ok (v2.30)
Going to read 'C:\Perl\cpan\Metadata'
  Database was generated on Wed, 24 Apr 2013 11:08:14 GMT
Running install for module 'DBD::Sybase'
Running make for M/ME/MEWP/DBD-Sybase-1.15.tar.gz
CPAN: Digest::SHA loaded ok (v5.84)
CPAN: Compress::Zlib loaded ok (v2.06)
Checksum for C:\Perl\cpan\sources\authors\id\M\ME\MEWP\DBD-Sybase-1.15
+.tar.gz ok

CPAN: Archive::Tar loaded ok (v1.90)
DBD-Sybase-1.15/
DBD-Sybase-1.15/README.freetds
DBD-Sybase-1.15/dbivport.h
DBD-Sybase-1.15/Makefile.PL
DBD-Sybase-1.15/PWD.factory
DBD-Sybase-1.15/CHANGES
DBD-Sybase-1.15/Sybase.pm
DBD-Sybase-1.15/dbdimp.c
DBD-Sybase-1.15/eg/
DBD-Sybase-1.15/eg/check-space.pl
DBD-Sybase-1.15/eg/Show.cgi
DBD-Sybase-1.15/eg/README
DBD-Sybase-1.15/eg/dbschema.pl
DBD-Sybase-1.15/CONFIG
DBD-Sybase-1.15/Sybase.h
DBD-Sybase-1.15/META.yml
DBD-Sybase-1.15/README.vms
DBD-Sybase-1.15/README
DBD-Sybase-1.15/Sybase.xs
DBD-Sybase-1.15/t/
DBD-Sybase-1.15/t/xblob.t
DBD-Sybase-1.15/t/utf8.t
DBD-Sybase-1.15/t/thread.t
DBD-Sybase-1.15/t/nsql.t
DBD-Sybase-1.15/t/screen.jpg
DBD-Sybase-1.15/t/multi_sth.t
DBD-Sybase-1.15/t/base.t
DBD-Sybase-1.15/t/_test.pm
DBD-Sybase-1.15/t/place.t
DBD-Sybase-1.15/t/main.t
DBD-Sybase-1.15/t/autocommit.t
DBD-Sybase-1.15/t/xblk.t
DBD-Sybase-1.15/t/login.t
DBD-Sybase-1.15/t/exec.t
DBD-Sybase-1.15/t/fail.t
DBD-Sybase-1.15/BUGS
DBD-Sybase-1.15/MANIFEST
DBD-Sybase-1.15/dbdimp.h
DBD-Sybase-1.15/dbd-sybase.pod
CPAN: File::Temp loaded ok (v0.22)
CPAN: Parse::CPAN::Meta loaded ok (v1.4404)
CPAN: CPAN::Meta loaded ok (v2.120921)

  CPAN.pm: Going to build M/ME/MEWP/DBD-Sybase-1.15.tar.gz

Set up gcc environment - 3.4.5 (mingw-vista special r3)
Please set SYBASE in CONFIG, or set the $SYBASE environment variable a
+t Makefile
.PL line 120, <IN> line 44.
Warning: No success on command[C:\Perl\bin\perl.exe Makefile.PL INSTAL
+LDIRS=site
]
CPAN: YAML::XS loaded ok (v0.39)
  MEWP/DBD-Sybase-1.15.tar.gz
  C:\Perl\bin\perl.exe Makefile.PL INSTALLDIRS=site -- NOT OK
Running make test
  Make had some problems, won't test
Running make install
  Make had some problems, won't install
Could not read metadata file. Falling back to other methods to determi
+ne prerequisites
[download]

C:\Perl>perldoc -l DBD::Sybase
No documentation found for "DBD::Sybase".
[download]

C:\Perl>perldoc -l MINGW
C:\Perl\site\lib\MINGW.pod
[download]

Did you read the error output on the install?

Please set SYBASE in CONFIG, or set the $SYBASE environment variable a
+t Makefile
.PL line 120, <IN> line 44.
[download]

See the README file, especially the section on Building.

It might make sense to submit a bug against the module to have it use the proper CPAN mechanism to prompt the user if it cannot find the proper environment variable.

--MidLifeXis

It might make sense to submit a bug against the module to have it use the proper CPAN mechanism to prompt the user if it cannot find the proper environment variable.

:) I disagree, 1)its a tangent nothing to do with the OP 2) death is preferable to prompting