If a question is about Perl and the answer is not either "use a hash" or "use a module that uses a hash", the answer is probably wrong.

Populate a hash with your numbers and then test for existence, something like untested:

my @numbers = qw(123 345 456 567 890);
my %hash;
$hash{$_}++ for @numbers;

for (1,56,123,567,8888) 
{ 
if ($hash{$_})  {print "Found $_\n" }
else           { print "Not found $_\n"; }

}
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--
Regards,
Helgi Briem
helgi AT decode DOT is