I have all of it working except the looping through @vidids.

Im not sure you have the rest working either. I use Oauth2, and so include a Authorization: Bearer ... header rather than a api key via LWP.

You dont check for an error return, part=items(viewCount) returns content of

 "error": {
  "errors": [
   {
    "domain": "youtube.part",
    "reason": "unknownPart",
    "message": "items(viewCount)",
    "locationType": "parameter",
    "location": "part"
   }
  ],
  "code": 400,
  "message": "items(viewCount)"
 }
[download]

and a return code of 400. You will want part=statistics instead. To limit the fields returned you use the fields= parm. And there is no requirement that the api returns all of the ids requested or in any certain order. you will want to get the id field as well fields=items/id,items/statistics/viewCount So you will want to save both the id and viewcount. a hash works well for this.

sub api_videos { 
use Data::Dumper; 
    my $ua=LWP::UserAgent->new(keep_alive=>1,timeout=>100); 

my @vidlist0=qw/
 bH4tEHg-Wtc ShI5jhe3bi4 bbpyN89Vquk EgJ5GGD_2QQ YoRnMC2MlqU 7M39G0Yxy
+dk 1ov2NQ2Sz5w HmourJ3O6Ss sWSzjBPI1cY czt_a0fKvFA 
 x6GDUIUHSqg 4oEWS33lt9M KlTwG3UNqE8 ACVgSl9OpIQ mbsGOyNjsNQ L2qpMI6mN
+pU 6a1Ziw0-4X4 3Z08nsbhlAY vMLGUrVyyMk pjmyy0qKN2o 
 qyXxrPTcFKE d2SFFHlHNCY akSp8m4JAnY AEDw975DAlM ypl033on69k LM7GxrK-h
+go L6qq5aVOEmc tGEnzlNkGKI Aq2QQYY8YSA ZnnzFSGGJP4
 Nt1qRbAlrCs cnGQ2nE3USI YuzE5jomGLk wSz2kCpuZ6E v40RcxCpvgM bUVLymf4c
+00 
 -_rQwhvJDd4 jmaB41hx8b0 lcLSo0dijv8 HtBbRvj2cfc lQVBX6aqC8o rbq4RZGP8
+YU
 qy5NfKg1fJo jtjOcSBBoiE aRhqb-pljGk iRbqaMfpOrA tSKGYQFwAHs 7sHXl8q7u
+DY
 d4u8Wj0xY7A Rtzk1I0BhSI
 x
 /; 
  my $vidlist=[]; 
  my $n=0; 
  my @vidlists=(); 
  my $testct=10; 
  my $back={}; 
  for my $vid (@vidlist0){
    $n++; 
    if ($n>$testct) {push @vidlists,$vidlist; $n=1; $vidlist=[];}
    push @{$vidlist},$vid;  
    }

  push @vidlists,$vidlist;  

  my $head='https://www.googleapis.com/youtube/v3/videos?fields=items/
+id,items/statistics/viewCount&part=statistics&id=';

  for my $vl (@vidlists){ 
    my $getline=$head.join(',',@{$vl}); 
    my $req = new HTTP::Request (GET => $getline 
                              ,HTTP::Headers->new(
                                                    'Authorization'   
+    => 'Bearer '.$agrp->{access_token} )
                              );
    my $request = $ua->request ($req);
  
    unless ($request->is_success) { 
       print "\n** Can't get -- :".$request->status_line."\n";
       print $getline."\n";
      } 
    else { 
         my $jsondata; 
         eval{ $jsondata=$json->allow_nonref->decode($request->content
+);} ;
         if ($@) { print 'json decode error:'.$@ ."\n"; } 
         elsif ($jsondata->{error}) { print Dumper(\$json); } 
         else { 
           for my $item( @{$jsondata->{items}} ) {
             $back->{$item->{id}}=$item->{statistics}{viewCount}; 
             } # item 
           } # no error 
        } # success  
    } # vl

for my $vid(@vidlist0) { 
  unless (exists $back->{$vid} ) {print "video $vid not returned\n";} 
  }
print Dumper({back=>$back});
}
[download]

result

video x not returned
$VAR1 = {
          'back' => {
                      'bH4tEHg-Wtc' => '39',
                      'EgJ5GGD_2QQ' => '40',
                      'mbsGOyNjsNQ' => '150',
                      'bUVLymf4c00' => '51',
                      'qy5NfKg1fJo' => '20',
                      'bbpyN89Vquk' => '22',
                      'Rtzk1I0BhSI' => '87',
                      'rbq4RZGP8YU' => '60',
                      'qyXxrPTcFKE' => '46',
                      'ZnnzFSGGJP4' => '66',
                      'AEDw975DAlM' => '69',
                      '7M39G0Yxydk' => '31',
                      'ACVgSl9OpIQ' => '89',
                      'wSz2kCpuZ6E' => '52',
                      'L6qq5aVOEmc' => '69',
                      'cnGQ2nE3USI' => '43',
                      'v40RcxCpvgM' => '50',
                      'ypl033on69k' => '63',
                      'tSKGYQFwAHs' => '51',
                      'jtjOcSBBoiE' => '170',
                      'pjmyy0qKN2o' => '236',
                      'vMLGUrVyyMk' => '151',
                      'LM7GxrK-hgo' => '405',
                      'ShI5jhe3bi4' => '30',
                      'jmaB41hx8b0' => '186',
                      'L2qpMI6mNpU' => '162',
                      'czt_a0fKvFA' => '152',
                      '1ov2NQ2Sz5w' => '19',
                      'sWSzjBPI1cY' => '58',
                      'YuzE5jomGLk' => '32',
                      'Nt1qRbAlrCs' => '57',
                      'akSp8m4JAnY' => '131',
                      'x6GDUIUHSqg' => '77',
                      'lcLSo0dijv8' => '62',
                      'lQVBX6aqC8o' => '36',
                      'tGEnzlNkGKI' => '93',
                      'aRhqb-pljGk' => '181',
                      'KlTwG3UNqE8' => '49',
                      'd2SFFHlHNCY' => '48',
                      '-_rQwhvJDd4' => '108',
                      '6a1Ziw0-4X4' => '71',
                      'HtBbRvj2cfc' => '52',
                      'd4u8Wj0xY7A' => '51',
                      'YoRnMC2MlqU' => '59',
                      '3Z08nsbhlAY' => '86',
                      '7sHXl8q7uDY' => '17',
                      'HmourJ3O6Ss' => '147',
                      '4oEWS33lt9M' => '38',
                      'Aq2QQYY8YSA' => '101',
                      'iRbqaMfpOrA' => '51'
                    }
        };
[download]