++ For the hash method, although your nested structure makes it look more complex than the other solutions. It can be made to look much simpler using a single level, and the fact that there won't be autovivification in boolean context: 

# equivalent to %is_valid = (ABA => 1, SCO => 1, ACC => 1...);
my %is_valid = map { $_ => 1 } qw( ABA SCO ACC PHC GHF ); 

if ($is_valid{$variable}) # Easy to read
{
  ...
}

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In reply to Re^2: Sparing multiple 'or's by Eily
in thread Sparing multiple 'or's by Denis

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