Maybe the core of your problem is that you have a string like this:

my $string = '+book +dog +cat';
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... and you want to transform it into

"+book", "+dog", "+cat"
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Then, the following code could do that:

my $string = '+book +dog +cat';
my @raw_params = split /\s+/, $string;
my @quoted_params = map { qq{"$_"} } @raw_params;
my $quoted_params_string = join ", ", @quoted_params;
print $quoted_params_string;
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Update: johngg++ spotted an error that resulted in pluses being added unnecessarily.

This is wat i tried, but not working because the receipts numbers have to be this way

my @recipients = ("+1234567890", "+1234567890");

my $sender = $CGI->param("sender");
my $phone   = $CGI->param("phonenumber"); # so am entering this way +1
+2344, +123344, +45454444 in textarea
my $message = $CGI->param("message");


my $rep = '';

if ($sender) {
    
my @raw_params = split /\s+/, $phone;
my @quoted_params = map { qq{"$_"} } @raw_params;
my $quoted_params_string = join ", ", @quoted_params;
my @recipients = ($quoted_params_string);
foreach my $recipient (@recipients) {
my $req = HTTP::Request->new(POST => 'https://api.twilio.com/2010-04-0
+1/Accounts/AC5b68......756/Messages.json');
$req->content_type('application/x-www-form-urlencoded');
$req->authorization_basic("AC5b686.....56", "cd3.......d");
$req->content("To=$recipient&From=$sender&Body=$message");


my $response = $ua->request($req);

if ($response->is_success) {
  $rep = "<p style='color: #29AB87;'>Messages Sent</p>";
} else {
  $rep = "<p style='color: #BF4F51;'>Nothing Sent</p>";
}
}
}
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From my cursory reading of the Twilio documentation of the Message API, it expects $message to contain a JSON message as in the examples.

You send some string in the Body parameter that may or may not be a properly URL-encoded JSON message that Twilio expects.

Also, concatenating strings does not make something x-www-form-urlencoded. You should properly URL-encode the parameters or look (for example) at the URL::Encode module for properly encoding all the parameters. Especially, your phone numbers contain the + character, which needs to be URL-encoded, for example as %22.

replace

my @raw_params = split /\s+/, $phone;
my @quoted_params = map { qq{"$_"} } @raw_params;
my $quoted_params_string = join ", ", @quoted_params;
my @recipients = ($quoted_params_string);
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with

my @recipients = $phone =~ /[+\d]+/g;
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