Dear fellow monks, your novice here.
I am trying to understand what goes on behind the scenes with the code posted below.
I keep getting
Use of uninitialized value in print at map001.pl line 61. (and at line 81)
How do I get the code to tell me the names of the key - value pairs so that I can reference them ?

# Perl program to demonstrate the  
# splitting into the hash 
  
#!/usr/bin/perl 
use strict; 
use warnings; 
 
 
# variables used for computations
my $linecount;
my $start = time;
my $column_count;
my $file_errors = 0;


my %distance;
my %consec_two;
my %consec_three;
my %adj_row;
my @prev;

#-----------------------------------------------------

my @items = (2,14,7,17,1,12,3,4,11,5,13,6,8,10,9,16,15,18);

print "@items\n\n";       

my @wrongsort = sort @items;
print "@wrongsort\n\n";   

@items = map {sprintf '%02u', $_ } @items;      
                            
                            
print "@items\n\n";       

@items = sort @items;        

print "@items\n\n\n";

        $column_count = @items;
        
        my ($odd)=(0);
        my ($even)=(0);
       
print "Column Count = ","$column_count\n";




map {$_ % 2 ? $odd++ : $even++} @items; 
                                      
print "Odd = ","$odd\n";
print "Even = ","$even\n";

print "\n\n";

my %odd_even;
        print "\%odd_even hash contents \t\t", %odd_even, "\n\n";     
+                                   
$odd_even{"$odd $even"}++;     
        print "\%odd_even hash contents \t\t", %odd_even, "\n\n";
        
        print "\%odd_even contents \t\t", $odd_even{0}, "\n\n";
                



# compute average for each row    # first adding them all
my %average;  
      my $sum;
      map {$sum += $_} @items;
      
      my $avg = $sum / @items; 
     
      $avg = ($avg - int($avg)) >= 0.5  ?  
             int($avg) + 1              :
             int($avg);
      
      $average{$avg}++;

 print "AVERAGE hash contents \t\t", %average, "\n\n";
 
 print "AVERAGE hash contents \t\t", $average{0}, "\n\n";
[download]

thankyou

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