Thank you for your reply. That's a nice way to match the rest.
I however, using the following as it seems to fit my needs-

while (defined(my $line = <$fh>)) {
    next if $line =~ /^access-list .*\bremark\b/;

    given ($line) {
        when (/^access-list/) {

            # take the next word followed by object-group
            /object-group\s/;
            my @after = split(/\s/,$');
            my @keys = @after;

            push @lists, {groups => \@keys, line => $line};
        }
...............
   }
}
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