open my $fd, '<', $file or die "Can't open file: $!";
while(my $line = <$fd>){
   # do stuff with line in $line
}

##</code><code>##

my @fields = split /\t/, $line; # split the line on tabs
# or 
my( $threadnum ) = $line =~ /Thread-(\d+)/; # grab the digits following Thread-