#!/usr/bin/perl

use strict;
use warnings;

sub isin {
    my $a = pop;
    for (@_) {
        if ($_ eq $a) {
            return 1;
        }
    }
    return 0;
}

my $string = "Trig";
if(isin(('Trig', 'Cos', 'Sin'), $string)) {
    print "Is in.\n";
}