Is there a better way to put data from one subroutine into another ? thanks,

Yes.

Have the first subroutine return its data in an array of lines, and then pass that array into the second. like this:

my @results = second_sub(first_sub(@stuff));

# time passes

sub first_sub {
  my @inputs = @_;
  my @results;
  # etc
  return @results;
}

sub second_sub {
  my @results;
  foreach my $line (@_) {
    # etc
  }
  return @results;
}
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In short, rather than writing data to a file, and parsing it in again, just keep it all in native Perl data structures. Simpler, less work, and a better design because you don't parse.