I have a program which, among other things, reads archived files containg the output of "show diagbus" on Cisco routers. The relevant strings I'm matching in my regex are:

L3 Engine: 0 - OC12 (622 Mbps)
L3 Engine: 1 - OC12 (622 Mbps)
L3 Engine: 2 - OC12 (622 Mbps)
L3 Engine: 4 - OC12 (622 Mbps)


Here's a code snippet: 
%router_of_interest = (router1 => "1",
                       router2 => "1",
                       router3 => "1",
                       router4 => "1"
                      );

while ($file = readdir(DIA)) {
    if ($file =~ /(.*)\.bbnplanet.net/) {
        $router = $1;
        next unless exists $router_of_interest{$router};

open(DIAFILE,"$dir/$file") || die "Cannot open $dir/$file: $!\n";
    while ($line = <DIA>) {
    chomp $line;
    if ($line =~ /^\s*L3 Engine: (\d+)/i){
        $engine = $1;

        if (grep(/$engine/,@{$HoL_engine{$router}}) != 1){
           push @{$HoL_engine{$router}}, $engine;
       }
     }
   }
   if (exists $HoL_engine{$router}){
       $engine{$router} = join(",",sort @{$HoL_engine{$router}});
   }
   else {
        $engine{$router} = "NA"; #GSR IOS version too old
      }
   }
}

foreach $key (sort keys %engine) {
print "$key - Engine $engine{$key}\n";
}

[download]
this successfully prints:

router1 - Engine 0,2,
router2 - Engine 1,2
router3 - Engine 2
router4 - Engine NA

...etc.

Except, it won't print instances of:

router1 - Engine 0

Something about pushing one "0" and nothing else into my HoL fails. Can anyone help a poor Monk out?

In reply to Puzzling Hash of Arrays problem by Tuna

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