#!/usr/bin/perl -w
use strict;

my @lines;
my $ave;

print "Enter an input file name: ";
chomp (my $infile = <STDIN>);

while (!(-e $infile)) {
	print "Invalid file name, Try again: ";
	chomp ($infile = <STDIN>);
}
print "\n";

print "Enter an output file name: ";
chomp (my $outfile = <STDIN>);

open (FIN,'<', $infile) or die "$!\n";
chomp (@lines = <FIN>);
open (FOUT, '>', $outfile) or die "$!\n";

while (<STDIN>) {
	$ave = average(<FIN>);
 	print FOUT $ave;
}
close FOUT;

sub average {
	my $sum = 0;
    my $size = @lines;
    $sum = $sum + $_ foreach @lines;
    $sum / $size;
}

sub largest {
	my $max;
	for (@lines){
    	$max = $_ if !$max || $_ > $max;
	} 
	$max
}