This is a puzzlement of the environment, not Perl syntax. I have done nothing creative. Simply run a piece of sample code. The following is a sample program from perldoc:

#--http://perldoc.perl.org/functions/tie.html 
# print out history file offsets
use NDBM_File;
tie(%HIST, 'NDBM_File', '/usr/lib/news/history', 1, 0);
while (($key,$val) = each %HIST) {
    print $key, ' = ', unpack('L',$val), "\n";
    }
untie(%HIST)
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Which, on fedora 9
Summary of my perl5 (revision 5 version 10 subversion 0) configuration: Platform: osname=linux, osvers=2.6.18-92.1.10.el5, archname=i386-linux-thread-multi uname='linux x86-6.fedora.phx.redhat.com 2.6.18-92.1.10.el5 #1 smp wed jul 23 03:56:11 edt 2008 i686 i686 i386 gnulinux '
produces:

[Perl]# perl testTie1.pl
Can't locate NDBM_File.pm in @INC (@INC contains: /usr/lib/perl5/5.10.
+0/i386-lin
ux-thread-multi /usr/lib/perl5/5.10.0 /usr/local/lib/perl5/site_perl/5
+.10.0/i386
-linux-thread-multi /usr/local/lib/perl5/site_perl/5.10.0 /usr/lib/per
+l5/vendor_
perl/5.10.0/i386-linux-thread-multi /usr/lib/perl5/vendor_perl/5.10.0 
+/usr/lib/p
erl5/vendor_perl /usr/local/lib/perl5/site_perl/5.10.0/i386-linux-thre
+ad-multi /
usr/local/lib/perl5/site_perl/5.10.0 /usr/local/lib/perl5/site_perl /u
+sr/lib/per
l5/site_perl .) at testTie1.pl line 2.
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My search produced bupkis:

[prompt]#  find / -name "NDBM_File*"
[prompt]# perl -V
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So bring in CPANplus, to install NDBM_File:

CPAN Terminal> m NDBM_File    
 1 Memoize::NDBM_File                  0.65     MJD       
 2 NDBM_File                           1.07     NWCLARK   
CPAN Terminal> install 2                        

Installing NDBM_File (1.07)
[ERROR] The core Perl 5.010000 module 'NDBM_File' can only be upgraded
+ from 0 to 1.07 by Perl itself (perl-5.8.9.tar.gz). Aborting install.

*** Install log written to:
  /root/.cpanplus/install-logs/NDBM_File-1.07-1239814025.log
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HUH!! ?? (perl-5.8.9.tar.gz)

It is always better to have seen your target for yourself, rather than depend upon someone else's description.

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