Since you know the records' individual fields to be delimited by \t, and to be of a fixed width, you can use either split or unpack to grab each field. I chose split just because it's a more common idiom.

my $infile = "filename.dat";
my @records;
{
    open my $fh , "<", $infile or die "Can't open $infile!\n$!";
    my @records = map { chomp; [ split /\t/ ] } <$fh>;    
}
{
    local $" = "\t";
    print "@{$_}\n" foreach @records;    
}
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Each record is held in an anonymous array, referenced by the top level array, @records.

Update: Be sure that if you turn this in as homework you've studied the idioms so that you can explain them. There's a good chance your professor hasn't yet covered everything I (intentionally) used in this example.