use strict;

my $count = 0;
my $filename = "/home/mj/newlogs$count.log";
open my $filehandle, ">", $filename
    or die "Couldn't create '$filename': $!";
... loop
print $filehandle $3;
...
close $filehandle;
$count++;

##</code><code>##

my $filename = "/home/mj/newlogs$count.log";

##</code><code>##

my $filename = "/home/mj/newlogs" . $count . ".log";