open (FILEHANDLE, "+<$dir/$header_file") or die "Couldn't open $dir/$header_file \n";
while (<FILEHANDLE>) {
$_ =~ s|solver_version_major_h.*|solver_version_major_h= $nums[0],|; 
$_ =~ s|solver_version_minor_h.*|solver_version_minor_h= $nums[1],|;
$_ =~ s|solver_version_fix_h.*|solver_version_fix_h= $nums[2],|;
print FILEHANDLE "$_";
}
close FILEHANDLE;