Input: 
4
tom 332211
harry 112233
ryan 445566
john 334455
jay
harry
ryan
kelly
john

Output:
Not found
harry=112233
ryan=445566
Not found

Code:

use strict;
use warnings;
use Data::Dumper;

my %phone_num;

while (my $line = <STDIN>)
{
   my $name;
   my $phone;
   
   
   next unless ($name, $phone) = $line =~/^\s*([a-zA-Z]+)\s+(\d+)*/; 

   if (defined $phone)  # A new phone book entry
   {
       $phone_num{$name} = $phone;
   }
   else                 # Just a name. 
   {
       if ($phone_num{$name})
       {
           print "$name=$phone_num{$name}\n";
       }
       else
       {
           print "Not found\n";
       }
   }
}