use strict; # forgot this in the original ;(
outer_loop
{
  my $headerStr;
  ... # some code that may or may not initialize $headerStr

  my @headerElements = split /\s+/, $headerStr if $headerStr;

  if(! @headerElements)
  {
    # Create content for use later.
    $headerElements[0] = 'some value';
    $headerElements[1] = 'some value';
    $headerElements[2] = 'some value';
  }

  $headerElements[2] =~ s/[<>,]//g;
  ... # other checks and tests of the array content follow.
}