#!/usr/bin/perl
use strict;
use warnings;
use Math::Pari qw/:int factorint sqrtint PARImat/;

my $N = '1' . '0' x $ARGV[0] . '1';

print "Result for $N is ", nearest_sqrt(  $N );

sub prime_factors {
    my $N = shift;
    my %p_fact = PARImat( factorint( $N ) ) =~ /(\d+)/g;
    return map { ($_) x $p_fact{$_} } sort { $a <=> $b } keys %p_fact;
}

sub nearest_sqrt {
    my $N = shift;
    my $sqrt = sqrtint( $N );
    my @factor = prime_factors( $N );
....