Dear Forum.
Today i wrote a code which is seek for positive or negative number in a line( only 1 in 1 line ), and i don't now why this is work. 
#!/usr/bin/perl -w
$sum=0;
$count=0;

open(INPUT,"meres.txt") or die "ERROR";
while($line=<INPUT>)

{
    chomp($line);
    if($line=~/([-\d]+(\d+)*)/){
        #print($1."\n");
        $sum+=$1;
        $count++;
    }
}
close(INPUT);
print $sum/$count;
print "\n";

[download]
Well, i understand what pieces i am using but i wonder the logic behind it.
Thanks for your answer

In reply to Why this is work? by Csonytii

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