#!/usr/bin/perl 
use strict;
use warnings;

my $file = "controls.txt";
    # always(!!!)  use the three argument form of open
open (FH, "<", $file) or die "Can't open $file for read: $!";
my @lines;
while (<FH>) {
    chomp;
    push (@lines, $_);
}
close(FH) or die "Cannot close $file: $!";

my %seen = ();
my @uniq = ();
foreach my $line ( @lines ) {
        unless ($seen{$line}) {
                #if we get here, we have not seen it before
                $seen{$line} = 1;
                push(@uniq, $line);
        }
}

print join(", ",@uniq) , "\n";    # see if it worked

##</code><code>##

1
1
2
3
3
3
3
3
5
5
6
6
7
7

##</code><code>##

1, 2, 3, 5, 6, 7