Perl can use the grep function as the equivalent of PHP’s in_array() function. Essentially
$found = grep $_ eq $my_value, @my_array
Note, the grep() function is world unto its own, it can do quite a bit more than just this. $found is actually $my_value if it finds it, which tends to evaluate to ‘True’ in Perl.
You can view more PHP-Perl statements here.