Here is a different technique that avoids the nasty regex that was growing out of control:

use warnings;
use strict;
use Spreadsheet::WriteExcel;

my $workbook = Spreadsheet::WriteExcel->new("data.xls");
my $worksheet = $workbook->add_worksheet();

$worksheet->write ("A1", 'Device');
$worksheet->write ("B1", '/var');
$worksheet->write ("C1", '/');
$worksheet->write ("D1", 'interleaved');
$worksheet->write ("E1", 'avm');
$worksheet->write ("F1", 'fre');
$worksheet->write ("G1", 'cs');
$worksheet->write ("H1", 'us');
$worksheet->write ("I1", 'sy');
$worksheet->write ("J1", 'id');
$worksheet->write ("K1", 'Date');

my $row = 1;

open inFile, '<', 'data.txt' or die "Couldn't open data.txt: $!";

while (<inFile>)
  {
  chomp;
  next if ! length $_;

  if (/logging to (.*?) is/i)
    {
    ++$row;
    $worksheet->write("A$row", "$_");
    print "\n$1 ";
    next;
    }
  elsif (/logging to (.*?) is/i)
    {$worksheet->write("B$row", "$1");}
  elsif (/(\d+)% \/var/i)
    {$worksheet->write("C$row", "$1");}
  elsif (/(\d+)% \//i)
    {$worksheet->write("D$row", "$1");}
  elsif (/(\d+)% Interleaved/i)
    {$worksheet->write("E$row", "$1");}
  elsif (/(\d+) (\d+) (\d+) (\d+) (\d+) (\d+)/i)
    {
    $worksheet->write("F$row", "$1");
    $worksheet->write("F$row", "$2");
    $worksheet->write("F$row", "$3");
    $worksheet->write("F$row", "$4");
    $worksheet->write("F$row", "$5");
    $worksheet->write("F$row", "$6");
    print "$1 $2 $3 $4 $5 $6 ";
    next;
    }
  else {next;}

  print "$1 ";
  }

close inFile;

$workbook->close ();
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