my $pattern = join '|',
              map quotemeta,
              @countries;

if ($country =~ /^(?:$pattern)$/) {
   print "True\n"
}

##</code><code>##

my ($pattern) = map qr/^(?:$_)$/,
                join '|',
                map quotemeta,
                @countries;

if ($country =~ $pattern) {
   print "True\n"
}