This:

$line =~ m/\s*(\S+)\s*(\S+)\s*(\S+)\s*(\S+)\s*/;
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is a really bad way to split a line on whitespace. It will do all sorts of things you don't want in edge case situations. See this Re: ('Re: ' x 6) How to remove the $1 hard coding and its parent thread.

my ($device, $bps, $sps, $msps ) = split ' ', $line;
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Is far more robust, self documenting, and also faster way to split a file like the one you have into fields.

Makes no difference to the functionality but:

sub PlotGraph
{ 
  my $worksheet = shift;
  my $col = shift;
  my $row = shift;
  my $chartTitle = shift;
  my $xAxisTitle = shift;
  my $yAxisTitle = shift;

# reads better to my eye and makes it easier to see the function(args)
+ 
# (also a bit faster FWIW)

sub PlotGraph
{ 
  my ( $worksheet, $col, $row, $chartTitle, $xAxisTitle, $yAxisTitle )
+ = @_;
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cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print