If you need to do this sort of operation (is $foo in @list) often, you should probably be using a hash rather than a list, even if your values are undef.

#!/usr/local/bin/perl

use strict; use warnings;

my @list = qw(frog turtle tadpole);
my $var = "turtle";

my %check_list;
@check_list{ @list } = ();

if( exists $check_list{ $var } ){
    print "found $var!\n";
}
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Obviously you could get rid of @list entirely above.