A regex isn't the right tool for the job. Since the table has fixed width, use substr or unpack to extract the cells; perlpacktut has an example.

If the width of the columns isn't known in advance, use a regex to find the column width by considering the first line, and use unpack/substr for the rest of the table.

Update: some example code. Trimming of leading/trailing whitespaces left as an exercise to the reader

use 5.010;
use strict;
use warnings;

my $head_line = <DATA>;

my @c_idx;
while ($head_line =~ /\S+/g) {
    push @c_idx, $-[0];
}

my $sep = <DATA>; # ignored;
while (<DATA>) {
    chomp;
    my @columns;
    for my $idx (0..$#c_idx) {
        if ($idx == $#c_idx) {
            push @columns, substr $_, $c_idx[$idx];
        }
        else {
            push @columns, substr $_, $c_idx[$idx], $c_idx[$idx+1] - $
+c_idx[$idx];
        }
    }
    use Data::Dumper;
    print Dumper \@columns;

}

__DATA__
Mod  Sub-Module                  Model              Serial     
---- --------------------------- ------------------ -----------
  1  Distributed Forwarding Card WS-F6700-DFC3CXL   SAL1434RLPY
  3  7600 ES+ DFC XL             7600-ES+3CXL       JAE14520N29
  3  7600 ES+T 20x1GE SFP        76-ES+T-20GQ       JAE145301XM
  5  Policy Feature Card 3       7600-PFC3CXL       JAE14330E6J
  5  C7600 MSFC4 Daughterboard   7600-MSFC4         JAE14320QBE
  6  Policy Feature Card 3       7600-PFC3CXL       JAE14330EAO
  6  C7600 MSFC4 Daughterboard   7600-MSFC4         JAE14320QA8
  7  Distributed Forwarding Card WS-F6700-DFC3CXL   SAL1433QHBR
  8  Distributed Forwarding Card WS-F6700-DFC3CXL   SAL1433QXF9
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