If you're really checking for $var being eq to one of many elements, a hash would work.

my %look_for = map { $_ => 1 } qw( a b ... );
if ( $look_for{ $var } ) { }
[download]

That said, I don't see anything wrong with using a regular expression, if it does what you want. I'd only think grep is a problem if you have a huge number of items to check. Maybe you want List::Util::first here?