thanks but it's not putting what i enter into terminal into that file.

Yes it does.

>perl a.pl
fasfd
dsfdasfdasf
dsafsdafdas
fdasfdasfs
^Z

>type perlogfile.rtf
fasfd
dsfdasfdasf
dsafsdafdas
fdasfdasfs
[download]

Perhaps you are peeking at the file before you stop adding to it, in which case you are suffering from buffering. Fix:

#!/usr/bin/perl

use 5.010;

use strict;
use warnings;

use IO::Handle qw( );

my $fn_log = 'perlogfile.rtf';

open(my $fh_log, '>>', $fn_log)
    or die("Can't append to log file \"$fn_log\": $!\n");
$fh_log->autoflush(1);

print($fh_log $_) while <STDIN>;
[download]