in reply to Piping Tail and while loops

Try something like this: 

#! perl -slw
use strict;
use threads;
use Thread::Queue;

$|=1;

sub tail {
    my( $file, $Q ) = @_;
    
    my $pid = open TAIL, "u:tail --follow=name $file |" 
        or die $!;
    print "pid:$pid";
    END{ kill 9, $pid }
    while( <TAIL> ) {
        $Q->enqueue( $_ );
    }
}

my $Q = new Thread::Queue;

my $t = threads->new( \&tail, $ARGV[ 0 ], $Q );

while( sleep 1 ) {
    print 'Here';
    printf "Got: %s", $Q->dequeue() while $Q->pending;
}

[download]

Sample output

## Create a file to tail

P:\test>start /b perl -le"$|=1; select( undef, undef, undef, 0.1 ), pr
+int $_, '-'x100 for 1 .. 10000;" > tmp\log

P:\test>387706 tmp\log
pid:276
Here
Here
Here
Here
Got: 11---------------------------------------------------------------
+-------------------------------------
Got: 12---------------------------------------------------------------
+-------------------------------------
Got: 13---------------------------------------------------------------
+-------------------------------------
Got: 14---------------------------------------------------------------
+-------------------------------------
Got: 15---------------------------------------------------------------
+-------------------------------------
Got: 16---------------------------------------------------------------
+-------------------------------------
Got: 17---------------------------------------------------------------
+-------------------------------------
Got: 18---------------------------------------------------------------
+-------------------------------------
Got: 19---------------------------------------------------------------
+-------------------------------------
Got: 20---------------------------------------------------------------
+-------------------------------------
Got: 21---------------------------------------------------------------
+-------------------------------------
Got: 22---------------------------------------------------------------
+-------------------------------------
Got: 23---------------------------------------------------------------
+-------------------------------------
Got: 24---------------------------------------------------------------
+-------------------------------------
Got: 25---------------------------------------------------------------
+-------------------------------------
Got: 26---------------------------------------------------------------
+-------------------------------------
Got: 27---------------------------------------------------------------
+-------------------------------------
Got: 28---------------------------------------------------------------
+-------------------------------------
Got: 29---------------------------------------------------------------
+-------------------------------------
Got: 30---------------------------------------------------------------
+-------------------------------------
Got: 31---------------------------------------------------------------
+-------------------------------------
Got: 32---------------------------------------------------------------
+-------------------------------------
Got: 33---------------------------------------------------------------
+-------------------------------------
Got: 34---------------------------------------------------------------
+-------------------------------------
Got: 35---------------------------------------------------------------
+-------------------------------------
Got: 36---------------------------------------------------------------
+-------------------------------------
Got: 37---------------------------------------------------------------
+-------------------------------------
Got: 38---------------------------------------------------------------
+-------------------------------------
Got: 39---------------------------------------------------------------
+-------------------------------------
Got: 40---------------------------------------------------------------
+-------------------------------------
Got: 41---------------------------------------------------------------
+-------------------------------------
Got: 42---------------------------------------------------------------
+-------------------------------------
Got: 43---------------------------------------------------------------
+-------------------------------------
Got: 44---------------------------------------------------------------
+-------------------------------------
Got: 45---------------------------------------------------------------
+-------------------------------------
Got: 46---------------------------------------------------------------
+-------------------------------------
Got: 47---------------------------------------------------------------
+-------------------------------------
Got: 48---------------------------------------------------------------
+-------------------------------------
Got: 49---------------------------------------------------------------
+-------------------------------------
Here
Here
Here
Here
Got: 50---------------------------------------------------------------
+-------------------------------------
Got: 51---------------------------------------------------------------
+-------------------------------------
Got: 52---------------------------------------------------------------
+-------------------------------------
Got: 53---------------------------------------------------------------
+-------------------------------------
Got: 54---------------------------------------------------------------
+-------------------------------------
Got: 55---------------------------------------------------------------
+-------------------------------------
Got: 56---------------------------------------------------------------
+-------------------------------------
Got: 57---------------------------------------------------------------
+-------------------------------------
Got: 58---------------------------------------------------------------
+-------------------------------------
Got: 59---------------------------------------------------------------
+-------------------------------------
Got: 60---------------------------------------------------------------
+-------------------------------------
Got: 61---------------------------------------------------------------
+-------------------------------------
Got: 62---------------------------------------------------------------
+-------------------------------------
Got: 63---------------------------------------------------------------
+-------------------------------------
Got: 64---------------------------------------------------------------
+-------------------------------------
Got: 65---------------------------------------------------------------
+-------------------------------------
Got: 66---------------------------------------------------------------
+-------------------------------------
Got: 67---------------------------------------------------------------
+-------------------------------------
Got: 68---------------------------------------------------------------
+-------------------------------------
Got: 69---------------------------------------------------------------
+-------------------------------------
Got: 70---------------------------------------------------------------
+-------------------------------------
Got: 71---------------------------------------------------------------
+-------------------------------------
Got: 72---------------------------------------------------------------
+-------------------------------------
Got: 73---------------------------------------------------------------
+-------------------------------------
Got: 74---------------------------------------------------------------
+-------------------------------------
Got: 75---------------------------------------------------------------
+-------------------------------------
Got: 76---------------------------------------------------------------
+-------------------------------------
Got: 77---------------------------------------------------------------
+-------------------------------------
Got: 78---------------------------------------------------------------
+-------------------------------------
Got: 79---------------------------------------------------------------
+-------------------------------------
Got: 80---------------------------------------------------------------
+-------------------------------------
Got: 81---------------------------------------------------------------
+-------------------------------------
Got: 82---------------------------------------------------------------
+-------------------------------------
Got: 83---------------------------------------------------------------
+-------------------------------------
Got: 84---------------------------------------------------------------
+-------------------------------------
Got: 85---------------------------------------------------------------
+-------------------------------------
Got: 86---------------------------------------------------------------
+-------------------------------------
Got: 87---------------------------------------------------------------
+-------------------------------------
Got: 88---------------------------------------------------------------
+-------------------------------------
Here
Here
Terminating on signal SIGINT(2)

[download]
Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail
"Memory, processor, disk in that order on the hardware side. Algorithm, algorithm, algorithm on the code side." - tachyon

In Section Seekers of Perl Wisdom