@HeaderGarbage = ('LD 20',
                  'PT0000 ',
                  ...
                  'CUST ',
                  'DATE ',
                  'PAGE ',
                  'DES  ');
my $reg = join '|', @HeaderGarbage;
my $HeaderRegex = qr/^$reg/;
...
while (my $line = <FILE>) {
  $line =~ s/$HeaderRegex//; # replace matching garbage
  ...