hmm, there are all sorts of problems with your code as is.

Firstly, you're not using strict or warnings. That's bad™

Secondly, you do an opendir, but then you do nothing with the directory handle. That's a bit pointless.

Next, in your open line, you refer to $infilename - which has not been previously defined (strict and warnings would have alerted you to this).

So... here is a canonical way to achieve what you seem to be asking (untested):

#!/usr/bin/perl
use strict;
use warnings;

my $file = '/path/to/file.txt';

open IN, "<", $file or die "Could not open $file:$!\n";

my $wanted;
while (my $line = <IN>) {
    if ($line =~ /(All avg = \d+)/) {
        $wanted = $1;
        last;   # get rid of this if you need/expect to match multiple
+ lines
    }
}
[download]

That should be enough to get you going.

Update: added the "last" to the code, as per suggestion from ikegami

Cheers,
Darren :)