I have a perl script which performs multiple external commands and prints the outputs from STDERR and STDOUT to a logfile along with a series of my own print statements to act as documentation on the process. My problem is that the STDERR repeats ~identical prints as example below. I'd like to capture this before it prints and replace with the final result for each of the commands i run. blocks evaluated : 0 blocks evaluated : 10000 blocks evaluated : 20000 blocks evaluated : 30000 ... blocks evaluated : 3420000 blocks evaluated : 3428776 Here's how I'm getting STDOUT and STDERR my $logfile = "Logfile.log"; #log file name #--- Open log file for append if specified --- if ( $logfile ) { open ( OLDOUT, ">&", STDOUT ) or die "ERROR: Can't backup STDOUT location.\n"; close STDOUT; open ( STDOUT, ">", $logfile ) or die "ERROR: Logfile [$logfile] cannot be opened.\n"; } if ( $logfile ) { open ( OLDERR, ">&", STDERR ) or die "ERROR: Can't backup STDERR location.\n"; close STDERR; open ( STDERR, '>&STDOUT' ) or die "ERROR: failed to pass STDERR to STDOUT.\n"; } and closing them close STDERR; open ( STDERR, ">&", OLDERR ) or die "ERROR: Can't fix that first thing you broke!\n"; close STDOUT; open ( STDOUT, ">&", OLDOUT ) or die "ERROR: Can't fix that other thing you broke!\n"; How do I access the STDERR when each print is occurring to do the replace? Or prevent it from printing if it isn't the last of the batch. Many Thanks in advance.