use strict;

# ...

my $exists =
  exists $hoh{ typo }{ attrib_1 };       # strict can't hear you scream...

# ... life goes on

my $number_of_entities = keys %hoh;      # BONK!


##</code><code>##

my @big_in_assoc_1 = grep keys %{$assocs_1{$_}} > 25, keys %assocs_2;

# ... tics later

my @relative_complement = grep !exists %assocs_1{$_}, keys %assocs_2;  # OUCH!

##</code><code>##

my $number_of_entities = grep defined $hoh{$_}, keys %hoh;     

##</code><code>##

my @big_in_assoc_1 =
  grep $assocs_1{$_} && keys %{$assocs_1{$_}} > 25,
  keys %assocs_2;