sub is_present {
    my $cluster = shift;
    scalar grep {/^\Q$cluster\E\.hosts$/o} @{$HoL{$cluster}};
}
[download]

TMTOWTDI is a vast understatement for functions like this

Update: On reflection, I should be testing for equality, not match. I changed the re above to do that, but here is a better way:

sub is_present {
    my $cluster = shift;
    scalar grep {$_ eq "$cluster.hosts"} @{$HoL{$cluster}};
}
[download]

After Compline,
Zaxo