Here's my snippet. This program reads the passwd file (or pseudo passwd file) and then reads a file in which to ignore users and compares the users in each. If it finds the user in the ignore file it skips that person and continues on. The last statement here is forcing the while loop to constantly skip the foreach loop after the very first time it hits the last statement. See below. passwd file has lines from your passwd file, and ignoreusers has a username, one per line. excuse the bad coding :)

  my $meglimit=10;
  my $debug=1;
  my $daylimit='15';
  my ($user, $name, $homedir, $total, $matched);

  open(IGUSERS, "$workdir/ignoreusers") || die "cannot open ignoreuser
+s file: $!";
  open(PASSWD, "passwd") || die "cannot open passwd file: $!";   
  while(<PASSWD>) {
    chomp;
    $matched=2;
    ($user, $name, $homedir)=(split /:/)[0,4,5];
    print "$user-$name-$homedir\n";
    foreach my $iguser (<IGUSERS>) {
     print "running foreach\n";
     chomp ($iguser);
        if ($iguser eq $user) {
       print "MATCHED-$iguser with $user\n";
       $matched=1;
       last;
     } else {
       print "MATCH FAILED-$iguser with $user\n";
       $matched=0;
     }
    }
    print "stuff\n";
    if ($matched==0) {
     chdir "$homedir" || die "cannot chdir to $homedir: $!";
     my $rawtotal=`du -smc * |grep total` || die "failed: $!";
     print "DEBUG: Scanned - $user\n" if $debug==1;
     $rawtotal =~ m/([0-9]+)/;
     $total = $1;
     if ($total > $meglimit) {
       print "DEBUG: $user exceeded cap: $total\n" if $debug==1;
       #&checkdb();
       #&notify();
       #&updatedb();
     }
    } else {
     print "something\n";
    }
    print "looping\n";
  }
  close(PASSWD);
  close(IGUSERS);
}
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