sub ReadTheEntireFile
{
  my $F = defined $_[0] ? $_[0] : '';
  $F =~ tr`<>*?\"\|\x00-\x1F``d;      # Remove illegal characters.

...

sub CreateFile
{
  defined $_[0] or return 0;
  my $F = shift;
  # Remove illegal characters from file name:
  $F =~ tr`<>*?\"\|\x00-\x1F``d;