my $data = q(0       ASDF
        ASEE
        ASEE

13      DERG
        DREG

28      QWER
        QWER

42      WERT
        WERT
        WERT

55      QWEASD
        QWEASD
        QWEASD
        QWEASD
);

open $hndl , "<", \(my $s = $data);
open $out , ">", \(my $formatted = '');
my $substitute_field;

READ_FILE:
while (my $line = <$hndl>) { 
	chomp $line;
## Ignore any lines that don't contain relevant text
	$line =~ /\S+/ or next READ_FILE;

	$line =~ /^\s*(\d+)(\s+)([A-Z]+)/ and do {
		$substitute_field = $1;
		print $out $substitute_field, $2 ,$substitute_field,"\n";
		next READ_FILE;
	}; 
## If we don't have a field to substitute move on
	defined $substitute_field or next READ_FILE;
## Must have valid line
	$line =~ s/^(\s*)([A-Z]+)/$1$substitute_field/;
	print $out $line,"\n";
	
} 

print $formatted;
close $hndl;
close $out;