split the lines on commas into an array, then compare only the fields you're interested in:

use warnings;
use strict;

my @currs;
my @lasts;
while (<DATA>) {
    @currs = (split /,/)[0..2, 7..8];
    my $same = 1;
    if (@lasts) {
        for (0 .. $#currs) {
            $same = 0 if $currs[$_] ne $lasts[$_];
        }
    }
    print unless $same;
    @lasts = @currs;
}

#0        ,1 ,2   ,3    ,4          ,5    ,6   ,7   ,8
#file_name,id,user,group,permissions,links,path,date,file_size
#file_name,id,user,                             date,file_size
__DATA__
foo,123,me,us,777,golf,/home/me,5/3/11,100
foo,123,me,them,666,four,/home/you,5/3/11,100
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