The problem is that in the third part of your for loop you are incrementing $i, and in your main loop you are assigning what you want it to be.

For the record I would never think of using a double-loop to solve this problem. Instead I might build a hash of arrays like this (untested) code: 

my %group2user;
foreach my $rec (@all_groups) {
  push @{$group2user{$rec->[0]}}, $rec;
}
foreach my $group_id (sort keys %group2user) {
  # Do whatever
}

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or else I would assume that the groups appeared grouped and work like this: 
my $old_id;
for my $rec (@all_groups) {
  if (not defined $old_id or $old_id <=> $rec->[0]) {
    # Spit out header
    $old_id = $rec->[0];
  }
  # Print user record
}

[download]
With either approach I push work down to Perl, and wind up with more reliable code. :-)

In reply to Re (tilly) 1: Nested For Loop giving me extra iterations by tilly
in thread Nested For Loop giving me extra iterations by jreades

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