my $sshport;
while ( $sshport !~ /^[1-9]\d+$/ || $sshport > 65535 ) {
   print " Please Enter valid ssh port number:\n";
   chomp( $sshport = <STDIN> );
}

##</code><code>##

while (<SSHD_CONFIG>){
    s/^Port.+/Port $sshport/i;
    s/^#Port\s.+/Port $sshport/i;
    print SSHD_CONFIG_NEW $_;
}

##</code><code>##

rename('sshd_config','sshd_config.old')
    or die "Can't rename sshd_config: $!";
rename('sshd_config.new','sshd_config')
    or die "Can't rename sshd_config.new: $!";