If I may suggest, a regex is not the best tool for the job here. Unless there is an overriding reason, it might be easier just to do something along the lines of:

my $filename = "blah.txt"; #replace as needed
rename($filename, $filename . '.bak') 
    or die("Unable to rename $filename to $filename.bak: $!\n");
open(INFILE, $filename . '.bak') 
    or die("Can't open $filename.bak for input: $!\n");
open(OUTFILE, '>' . $filename) 
    or die("Can't open $filename for output: $!\n");
  my $linecount = 0;
  while ($line = <INFILE>) { 
    print(OUTFILE $line) if ($linecount);
    $linecount++;
  }
close(INFILE);
close(OUTFILE);
[download]

Two references that cover this and more that I use frequently are the perl FAQs and Perl Cookbook, and there are others here and about.

Hope that helps. I look forward to seeing the responses of others as well.