#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my %phone_num;

while (my $line =<DATA>)
{
   my $name;
   my $phone;
   
   # this throws away malformed lines, like "4 (represents..."
   
   next unless ($name,$phone) = $line =~/^\s*([a-zA-Z]+)\s+(\d+)?/; 

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

print "\nJust to show what phone_num hash is:\n";
print Dumper \%phone_num;

=Program Output:
Not found
john 334455
Not found

Just to show what phone_num hash is:
$VAR1 = {
          'harry' => '112233',
          'tom' => '332211',
          'ryan' => '445566',
          'john' => '334455'
        };
=cut

__DATA__
4 (represents no. of entries in phone directory)
tom 332211
harry 112233
ryan 445566
john 334455
jack
john
jay
4576654  this is also junk line (just a number)