For a decent number of files, you can use:

sub get_files_count {
    my ($dir) = @_;
    opendir my $dir_h, $dir or return 0;

    # Number of files
    return scalar grep { -f "$dir/$_" } readdir $dir_h;

    # Number of files+dirs
    return scalar @{[readdir $dir_h]} - 2;
}

print get_files_count('./');
[download]

Or for a larger number of files, you can use:

sub get_files_count {
    my ($dir) = @_;
    opendir my $dir_h, $dir or return 0;
    my $files = 0;
    while(defined(my $file = readdir $dir_h)){
        if($file eq '.' or $file eq '..'){ next; }

        # Uncomment the bellow line to count only files
        # next unless -f "$dir/$file";

        ++$files;
    }
    closedir $dir_h;
    return $files;
}

print get_files_count('./');
[download]