SERIAL NUMBER:    nnn 
DIE COORDINATES:  X=xx,Y=yy
[several lines of measurement values]
END OF TEST
BIN NAME:         FAIL_FUNCTIONAL_TEST
RESULT:           FAIL
SERIAL NUMBER:    nnn 

##</code><code>##

#!/usr/bin/perl

use warnings;
use strict;

die "Usage: $0 <file1> <file2>\n" unless scalar(@ARGV)>1;

undef $/;
my @f1 = split(/(?=(?:SERIAL NUMBER:\s+\d+))/, <>);
my @f2 = split(/(?=(?:SERIAL NUMBER:\s+\d+))/, <>);

die "Error: file1 has $#f1 serials, file2 has $#f2\n" if ($#f1 != $#f2);

foreach my $i (0 .. $#f1) {
	print (($f2[$i] =~ m/RESULT:\s+PASS/) ? $f2[$i] : $f1[$i]);
}

print STDERR "$#f1 serials found\n";