If your log file are organized in that order, (I mean "WORKSTATION" and "exit code" come one by one and in a fixed order), then you can just use:

#!/usr/bin/perl
use warnings;
use strict;

open my $fh, '<', 'log.txt' or die "cant open log.txt:$!";

my $workstations;
while (<$fh>) {
    next if /^\s*$/;
    if (/(WORKSTATION\d+)/) {
        $workstations = "$1(Line $.)";
    } elsif (/(User program exit code:\s*\d+)/) {
        print "$workstations $1(Line $.)\n";
    }
}
[download]

If "WORKSTATION.." is at the beginning of a line as it seems to be in your example, change the regex to ^(WORKSTATION\d+) which makes it better/faster to suit your problem. so does 'User program exit code:' line...

Regards

lihao(XC)