use strict;
use diagnostics;
use warnings;

while (1) {
    print "Enter an input file name: ";
    chomp (my $choice = <STDIN>);
    open (my $fh, '<', "C:/temp/tsukk/$choice")                     #   [pryrt] use lexical filehandles
        or die "error opening $choice: $!";                         #   [pryrt] check for errors; if you don't want this, "use autodie;" above

    # my @array; while (my $data = <$fh>) { push @array, $data; }   #   [AnomalousMonk]'s [id://1203631] 'better yet': bring my @array into the while(1)...
    my @array = <$fh>;                                              #   [AnomalousMonk]'s [id://1203631] 'simply': slurp the whole file by giving <> list context

    my $use_brostad = 1;                                            #   set to 1 to use [brostad]'s, else false to use the anonymous suggestion
    my ($largest, $smallest) = (-9e9,9e9);                          #   initialize to the wrong extremes
    if($use_brostad) {
        ($largest, $smallest) = (sort {$b <=> $a } @array)[0,-1];   #   [brostad]'s [id://1203655]: reverse sort, return the first and last elements
    } else {
        for my $v (@array) {                                        #   [anonymous monk]'s [id://1203660]: single pass through loop, without sorting; more efficient than brostad's single sort
            $largest = $v   if $v > $largest;
            $smallest = $v  if $v < $smallest;
        }
    }

    print "\nThe largest number is: ";
    print $largest, "\n";                                           #   [pryrt]: largest is now scalar, not array
    print "The smallest number is: ";
    print $smallest;                                                #   [pryrt]: smallest is now scalar, not array
    print "The average of the numbers is: ";
    printf "%.1f\n", my $average = average(@array);                 #   [pryrt]: only call average() once per dataset
    print "\n";

    foreach (@array) {
        chomp;
        if ($average > $_) {
            print "$_\t is below average.\n";
        } elsif ($average < $_) {
            print "$_\t is above average.\n";
        } elsif ($average == $_) {                                  #   [AnomalousMonk]'s [id://1203631]'s fix: comparison, not assigment
            print "$_\t is equal to average.\n";
        }
    }

    print "\nDo it again? (Yes or No): ";
    chomp (my $yesno=<STDIN>);

    if($yesno ne 'Yes') {
        print "Goodbye.\n";
        exit;
    }
}

sub average {
    if (@_) {                                                       #   [pryrt]'s [id://1203627]
        my @temp = @_;
        my $sum = 0;
        foreach (@temp) {
            $sum = $sum + $_;
        }
        return $sum/@temp;
    }
}