When you use a back-ticked command line to assign a string to a perl variable, the string includes the final line-feed character that was printed at the end by the shell command. So if you plan to use the string as a file name in an open statement, you need to "chomp" it:

my $date =`/bin/date +'%m%d%y'`;
chomp $date;

my $LOG = "log.$date";

# another way to do that is to use perl internals instead of a sub-she
+ll:

{
  my ($d,$m,$y)=(localtime)[3..5];
  my $perldate = sprintf "%02d%02d%02d", $m+1, $d, $y-100;

  die "This should never happen: $perldate != $date" 
      if $perldate ne $date;
}
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As for your question 3, I'm not quite sure about your intention, but I think the best way to start is by using a regex match and capture:

while (<HANDLE>) {
    next unless ( /FREEZING media id (.*)/ );
    print "I am FREEZING $1\n";
}
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(BTW, when using date strings in file names, I like to arrange them as "%y%m%d", so they sort nicely.)

update: Forgot to mention: when using a regex match in the while loop as shown above, you don't need to open a pipeline that runs the data through a separate "grep" process -- perl does the grep for you, by ignoring the lines that don't match the regex.