print "$., $line"

##</code><code>##

10
15: 1
15: hw
15: r
15: u
15: hi
15: 2
15: hw
15: r
15: u
15: hi
15: 3
15: hw
15: r
15: u

##</code><code>##

while (my $line = <MYFILE>) {
   ... code in loop ...
}