Thanks ar0n. I see your point about the \w.

I've also tried printing $1.

So the regex isn't matching. I replaced mine with yours.

my $now = time;
$log_start=scalar localtime $now -1 * 86400;
print "Log start = $log_start\n";
$log_start=~ s/^\w+\s+(\w+\s\d{1,2}\s\d{1,2}:\d{1,2}:\d{1,2})\s\d{4}$/
+$1/i;
 
print "Modified Log start = $1\n";
[download]

update

Thanks to ar0n in CB, the correct regex is:

$log_start=~ s/^\w+\s+(\w+\s+\d{1,2}\s\d{1,2}:\d{1,2}:\d{1,2})\s\d{4}$
+/$1/i;
[download]