>type foo.pl
my $logfile = 'foo.log';
open(my $log_fh, ">>", $logfile) or die "Can't open logfile: $!\n";
print $log_fh scalar(localtime), "\n";

>type foo.log
The system cannot find the file specified.

>perl foo.pl

>type foo.log
Thu Feb 21 17:59:01 2008

>perl foo.pl

>type foo.log
Thu Feb 21 17:59:01 2008
Thu Feb 21 17:59:05 2008