tail-f.pl

#!/usr/bin/env perl
use strict;
use warnings FATAL => "all";

# http://perldoc.perl.org/functions/seek.html
# tail -f

my $file = shift or die;
open my $fh, "<", $file or die "open $file: $!";

for (;;) {
    my ($pos, $line);
    for ($pos = tell $fh; $line = <$fh>; $pos = tell $fh) {
        print $line;
    }
    select undef, undef, undef, 0.3;
    seek $fh, $pos, 0;
}

tail-f2.pl

#!/usr/bin/env perl
use strict;
use warnings FATAL => "all";
use Sys::Hostname 'hostname';
use POSIX 'strftime';

# http://perldoc.perl.org/functions/seek.html
# tail -f

my $file = shift or die;
open my $fh, "<", $file or die "open $file: $!";
my $host = hostname;

for (;;) {
    my ($pos, $line);
    my $time = strftime("%F %T", localtime);
    for ($pos = tell $fh; $line = <$fh>; $pos = tell $fh) {
        print "$time [$host] $line";
    }
    select undef, undef, undef, 0.3;
    seek $fh, $pos, 0;
}