iana,
Ok - first a matter of style, I prefer:

my $logtype = $singlefilter[0]->[0];
# or 
my $Regex_Event = $singlefilter[0][1];
[download]

Back to your problem with pop. You are removing an array reference and assigning it to an array - you need to dereference at the same time:

my @singlefilter = @{ pop @filter };
my $logtype      = $singlefilter[0];
[download]

Cheers - L~R