As Corion suggested, use a LIKE query

# Remove non-alphanumeric characters 
# and replace them with spaces
$title =~ s/[^\w| ]/ /g;    
my @words = split /\s+/, $title;
my $filename = join '-',$date,@words;
               
# check to see if filename is being used
my $table = 'FILENAMES';
my $sql   = "SELECT filename FROM $table 
             WHERE filename LIKE ?";
my $res = $dbh->selectall_arrayref($sql,undef,$filename.'%');
my %hash = map {$_->[0]=>1} @$res;

my $i='';
while ( exists $hash{$filename.$i.'.html'} ){
  ++$i;
  ++$i if $i==1;
}
my $sql_i = "INSERT INTO $table (filename) VALUES (?)";
$dbh->do($sql_i,undef,$filename.$i.'.html');
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