Why not

my @keywords = keywords( join '', @raw_power );
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? Or, if you don't need the separate lines,

my $raw_power;
{
  local $/;  # get ready for slurpage
  open(DAT, $data_file) || die("COULD NOT OPEN FILE");
  $raw_power = <DAT>;
  close(DAT);
}

my @keywords = keywords($raw_power);
[download]