Premisions problem

I have a question about premisions.
I have a domain hosted by a hosting company, and when I let perl make a 
file and chmod it to 0711 it is posible for my to read the file whit 
perl, and to read the file when I'm loged in to the server on FTP.
But other domains on the same server can not read this file whit perl, 
what is good.
But now I have ad home a personal webserver on my laptop and whem I 
greate a file exactly as subscribet as above I can only read it whit 
perl but not when i'm loged in to server on FTP, then my premisions are 
not corect.

What is the diverence between my peronal server and the hosting 
company's server.
Is it becose I havent setup virtualhosts and the hosting company dus 
have set ip up.

Any help wil be great.