use strict;
use warnings;

my $headerCt = 1;
my $dataFile = q{xxx.dat};
open my $dataFH, q{<}, $dataFile
   or die qq{open: < $dataFile: $!\n};

my $discard = <$dataFH> for 1 .. $headerCt;

while ( <$dataFH> )
{
    my ( $col1, $col4, $col8 ) =
       ( split m{\t} )[ 0, 3, 7];

    # Do something here with your extracted columns.

}

close $dataFH
   or die {close: < $dataFile: $!\n};