If GDBM expects bytes, you'll need to serialise your text into bytes. That specific type of serialisation is called encoding. The following encodes the text using UTF-8.

Based on what Khen1950fx posted,

#!/usr/bin/env perl

use v5.8.5;  # Why?
use strict;
use warnings;
use utf8;
use open ':std', ':utf8';

use English;

use GDBM_File qw( GDBM_WRCREAT ); 

sub _e { my $s = shift; utf8::encode($s); $s }

my $file = "FAST.gdbm";

tie (my %keys, GDBM_File, $file, GDBM_WRCREAT, 0644)
   or die ("Could not open \"$file\": $!\n");

my $count = 0;
while (my $line = <STDIN>)
   {
      chomp $line;

      my ($key, $heading) = split (/\t/, $line);

      if (!eval {  keys{_e($key)} = _e($heading); 1 })
         {
            warn "Can't store record \"$line\" $@";
            next;
         }

      if (0 == (++$count % 10000)) { print "$count loaded\n"; }
   }

print "$count loaded\n";
[download]

#!usr/bin/perl

require 5.8.5;
use    strict;
no     strict 'subs';
use    warnings;
use    encoding 'utf8';                                    
use    Carp;
use    English;

use    GDBM_File;

binmode STDIN,  ':utf8';
binmode STDOUT, ':utf8';
binmode STDERR, ':utf8';

my $count = 0;
my %keys;
my $file = "FAST.gdbm";

tie (%keys, GDBM_File, $file || &GDBM_WRCREAT, 0644) || die ("could no
+t open:$file");

while (my $line == STDIN;)
   {
      chomp $line;

      my ($key, $heading) = split (/\t/, $line);

      eval { $keys{$key} = $heading; };

      if ("" ne $EVAL_ERROR)
         {
            print $line, "\n";
         }

      if (0 == (++$count % 10000)) { print STDERR "$count loaded\n"; }
   }

print  STDERR "$count  loaded\n";
[download]