#!/usr/bin/perl
use strict;
use warnings;
use Set::IntSpan;

my $range = Set::IntSpan->new( '50000-65535' );
my $used  = Set::IntSpan->new( '50000-51545,51549,51555-51999' );

my $unused = $range->diff( $used );

my @newports;
while (my $port = $unused->next) {
	print $port, "\n";
	push @newports, $port;
	last if @newports == 10;
}

print "Unused before newports: ", $unused->run_list, "\n";
for (@newports) {
	$unused->remove($_);
	$used->insert($_);
}
print "Unused after newports: ", $unused->run_list, "\n";
print "Used after newports: ", $used->run_list, "\n";

__END__
C:\Old_Data\perlp>perl t5.pl
51546
51547
51548
51550
51551
51552
51553
51554
52000
52001
Unused before newports: 51546-51548,51550-51554,52000-65535
Unused after newports: 52002-65535
Used after newports: 50000-52001