deep submerge,
Chances you are not using DB_File.

#!/usr/bin/perl
use strict;
use warnings;

use DB_File;  # This line is really important
tie my %HASH, 'DB_File', 'file' or die $!;
[download]

If that still gives you the same error than it means you likely typo'd it as pointed out by BrowserUk. Minor update to give credit to BrowserUk for other possibility