use Tk;
use strict;
use warnings;

my $mw=new MainWindow;
my @header = ("FHT_neg45","FHT_0","FHT_45","FHT_90","OHT_neg45","OHT_0","OHT_45","OHT_90");
my $button = $mw->Button(-text=>"temp",
	-command=> \&button)->pack();
MainLoop;

sub button {
	#Read BJSFM_out.prn into an array @data
	my $filename="BJSFM_out.prn";
	open my $fh, '<', $filename or die "Can't find $filename!";
	my $string="1DO YOU WANT INSTRUCTIONS?";
	my @data= map {chomp; $_} <$fh>;
	my $n=0;
	foreach my $line (@data) {
		if ($line eq $string) {
			$line = $header[$n];
			$n++;
		}
	}
	open my $write_fh, '>', 'temp.txt' or die $!;
	print $write_fh join "\n",@data;
	close $write_fh;
}