If you have Perl 5.10 you can do

if ($var ~~ [ 'a', 'b', ... ]) {
  ...
}
[download]

or

my @ok = ('a', 'b', ...);
if ($var ~~ @ok) {
  ...
}
[download]

This is more efficient than grep because it doesn't try to match every element.

In earlier versions you can do

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

lodin