use IO::File;
use IO::Socket;
use IO::Select;

my $file = '/tmp/test_file';

my $sel = IO::Select->new;

my $pos = -s $file;
my $fh = IO::File->new;

# read the file a first time if you like . . .
# Add IO::Socket objects to $sel

if ($pos < -s $file) {
    $fh->open($file, 'r') or die $!;
    $fh->seek($pos, 0);
    $sel->add($fh);
}

{
    my @ready = $sel->can_read;
    for (@ready) {
        if ($_ eq $fh) {
            print <$fh>;
            $sel->remove($fh);
            $pos = $fh->tell;
            $fh->close();
        }
        else {
            # do socket things
        }
    }

    if ($pos < -s $file) {
        $fh->open($file, 'r') or die $!;
        $fh->seek($pos, 0);
        $sel->add($fh);
    }

    last if end_condition(); # for some end condition
    redo;
}