Here is a way to store all the information in a hash and deal with those new lines:

use strict;
use warnings;
use Data::Dumper;
use List::Util qw(min max sum);

my %hash;
my @files = ('file1.txt','file2.txt');
for my $file (@files) {
    open(my $fh,"<",$file) or die "$file: $!";
    while (my $line = <$fh>) {
        chomp $line;
        next unless $line;
        my @items = split(/\s+/,$line);
        my $key = shift @items;
        my $total = shift @items;
        $hash{$key}{'sum'} += $total;
        push(@{ $hash{$key}{'points'} }, @items );
    }
    close($fh);
}
for my $key (keys %hash) {
    my $points = $hash{$key}{'points'};
    $hash{$key}{'min'} = min(@$points);
    $hash{$key}{'max'} = max(@$points);
    $hash{$key}{'avg'} = $hash{$key}{'sum'} / @$points;
    # to print the points
    print join(' ',@$points) . "\n";
}
print Dumper(\%hash);
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Output for one of the keys:

'8' => {
       'sum' => '29.489759'
       'min' => '2.940214',
       'max' => '3.083707',
       'avg' => '2.9489759',
       'points' => [
                     '3.011583',
                     '2.943297',
                     '2.940214',
                     '2.955738',
                     '2.968009',
                     '3.083707',
                     '2.958022',
                     '2.957737',
                     '2.982671',
                     '2.990788'
                   ],
     },
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