My attempt at calculating prime numbers in perl, without loops, using recursion.

prime-calc.pl

#!/usr/bin/env perl
# Just a little code to test for prime numbers
# Originally posted to my blog at www.jbldata.com

use strict;
use warnings;
use 5.010;
 
$DB::deep = 500;
$DB::deep = $DB::deep; # Avoids silly 'used only once' warning
 
no warnings "recursion";
 
# Identify primes between ARG0 and ARG1
 
my ($x, $y, $re_int, $result);
my ($prime, $is_int);
 
$x = $ARGV[0];
$y = $ARGV[1];
 
 
$is_int = sub {
    my $re_int = qr(^-?\d+\z);
    my ($x) = @_;
    $x =~ $re_int
      ? 1
      : 0;
};
 
$prime = sub {
    my ( $x, $y ) = @_;
    if ( $y > 1 ) {
        given ($x) {
            when ( $is_int->( $x / $y ) ) {
                return 0;
            }
            default {
                return $prime->( $x, $y - 1 );
            }
        }
    }
    else { return 1; }
};
 
$result = sub {
    my ( $x, $y ) = @_;
    if ( $x <= $y ) {
        if ( $prime->($x, $x-1) ) {
            say $x;
        }
        $result->( ( $x + 1 ), $y );
    }
};
 
 
$result->($x, $y);