my $regex = join '|', @all_the_different_values;

  if ( $data =~ /$regex/ ) . . .

##</code><code>##

  if ( $data =~ /^($regex)$/ ) . . .

##</code><code>##

  my %set;
  @set{ @all_the_different_values } = (); # make the set

  if ( exists $set{ $data } ) . . .