Smart-matching seems to work OK.

use 5.010;

my @set = qw/banana plum apple strawberry pear/;

my $var = "apple";
if ($var ~~ @set) {
    say "yes";
}
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There are also hashes which might be a tad faster if your set is large.

my %set = map { $_ => 1 } qw/banana plum apple strawberry pear/;
if (exists $set{$var}) {
    say "yes";
}
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