if ($expire < 1 ||  14 < $expire || int $expire != $expire) { die "Don't tamper with me!"; } or

my %check;
undef @check{1..14};

if (! exists $check{$expire}) { die "Don't tamper with me!"; }
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or

if ($expire !~ /^(?:[1-9]|1[0-4])$/) { die "Don't tamper with me!"; }
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or

use Quantum::Superpositions;

if ($expire != any(1..14)) { die "Don't tamper with me!"; }
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and many other ways.