calculating the difference in value between data

Step three in this code calculates the difference between the one value and the next.

the results shown :
232      356      434      767      786      854      avg 571.50      group 0011100210
232      124      78      333      19      68      avg 142.33      

the second line is the difference between the numbers on the first line.

The first entry on the second line reads 232. This should read 0, as we dont need the value from the start here.
Could the code be altered to reflect this ?

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use List::Util qw(sum);
 
##### Open files
open(my $IN,"invim2.vim") or die "Could not open input: $!\n";
open(my $OUT,">outvim2.vim") or die "Could not open output: $!\n";
 
my @avgs1;
my @avgs2;
my ($maxavg1, $minavg1, $maxavg2, $minavg2);
 
##### Step 1: read a line, and split it on comma
while(<$IN>){
        chomp;
        my @arr = split /,/;
        next unless @arr;
 
 
        # discard 1st and 2nd last and last item
        shift @arr; 
	pop @arr;
	pop @arr;
	# pop @arr;
 
 
        ##### Step 2: Sort data into ascending order
        @arr = sort {$a <=> $b} @arr;
        print "arr @arr\n";
 
 
        ##### Step 3: Calculate difference between neighboring pairs
        my @diff = ($arr[0], map {$arr[$_] - $arr[$_-1]} (1..$#arr));
        print "diff @diff\n";
 
 
        ##### Step 4: Calculate amount in each group
        my @groups = (0)x10;
        foreach my $a (@arr) {
                $groups[$a/100]++;
        }
        print "group @groups\n";
 
 
        ##### Step 5: Calculate average
 
        my $avg1 = sum(@arr)/@arr;
        printf "arr avg %.2f\n", $avg1;
        if(!$maxavg1 || $avg1 > $maxavg1) { $maxavg1 = $avg1; }
        if(!$minavg1 || $avg1 < $minavg1) { $minavg1 = $avg1; }
        push @avgs1, $avg1;
 
        my $avg2 = sum(@diff)/@diff;
        printf "diff avg %.2f\n", $avg2;%.2f
        if(!$maxavg2 || $avg2 > $maxavg2) { $maxavg2 = $avg2; }
        if(!$minavg2 || $avg2 < $minavg2) { $minavg2 = $avg2; }
        push @avgs2, $avg2;
 
        ##### Step 6: Print results
	
	
 
 
        print $OUT join("\t", @arr) . "\tavg " . sprintf("%.2f\t", $avg1) . "group " . join("", @groups) . "\n";
        print $OUT join("\t", @diff) . "\tavg " . sprintf("%.2f\t", $avg2) . "\n";
        print $OUT "\n";
}
 
 
	printf "input: maxavg %d minavg %d avgavg %d\n", $maxavg1, $minavg1, sum(@avgs1)/@avgs1;
	printf $OUT "For data values:\t\t avg avg %.2f\t maximum avg %.2f\t minimum avg %.2f \n", sum(@avgs1)/@avgs1, $maxavg1, $minavg1 ;
	printf "diff: maxavg %d minavg %d avgavg %d\n", $maxavg2, $minavg2, sum(@avgs2)/@avgs2;
	printf $OUT "For data difference values:\t avg avg %.2f\t maximum avg %.2f\t minimum avg %.2f \n", sum(@avgs2)/@avgs2, $maxavg2, $minavg2, ;
 
	
 
close($IN);
close($OUT);

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