Perl reprompt user input until get exact expected input - perl

Question

How to make script very interactive?
Script purpose:
Get user entered number and find mod via get_mod_val function; if it returns 1 then say "good" and exit the script; if it returns 0, then ask user to enter odd number.
Validation:
accept only numbers, no character, decimal, special characters.
do not end the script until user has entered the odd number.
The following code works fine; it follows above validation point 1 rules, but it is not very interactive as per our requirement law. When above rules fails, script exits and we need to execute the script again.
How can we make the following code very interactive?
$ip_no = $ARGV[0];
if ($ip_no!="") {
$get_mod_op = get_mod_val($ip_no);
if ($ip_no =~ /\D/){
print "Entered number only.....";
exit;
}else{
if ($get_mod_op==1) {
print "Good odd number(${get_mod_op}): ${ip_no} ";
exit;
}else{
print "Good even number(${get_mod_op}): ${ip_no} ";
exit;
}
}
}else{
print "Enter number.";
exit;
}
Thank to all, finally i have done the code with your suggestions, Following snippet reached my requirement, review the code and advise for optimization.
if ($ARGV[0] != "") {
$user_ip = $ARGV[0];
}elsif (($ARGV[0] =~ /\D/ ) || ($ARGV[0] eq "") ){
print "Enter odd number only: ";
$user_ip = <STDIN>;
}else{
$user_ip = <STDIN>;
}
do{ #get mod value, if mod_off is 1 then entered number is odd otherwise ask user to enter the odd number
$mod_off = find_mod_val($user_ip);
if (($user_ip == "") || ($user_ip eq "") || ($user_ip eq "") || ($mod_off == 0)) {
print "Enter odd number only: ";
$user_ip = <STDIN>;
}
}until($mod_off == 1);
print "Good odd number ${user_ip}";
sub find_mod_val($user_ip){
return $user_ip%2;
}
__END__

Answer 1

TIMTOWTDI, this time with recursion! The benefit is that you can reuse the function to validate other inputs too. I guess you could make a sub that wraps a loop, but c'mon this is fun!
sub get_input {
my ($message, $valid) = #_;
print "$message: ";
chomp(my $response = <>);
unless( $response =~ $valid ) {
print "Invalid response!\n";
$response = get_input($message, $valid);
}
return $response;
}
my $response = get_input("Enter a number", qr/^\d+$/);
print "Got: $response\n";

Answer 2

Don't use ARGV[0] and read from STDIN (so you need to run your script and type the word you want). I have rewritten your code:
my $finish = 0;
while( ! $finish ) {
print "Enter number.";
my $ip_no = <STDIN>;
chomp($ip_no);
$get_mod_op = get_mod_val($ip_no);
if( $ip_no =~ /\D/ ){
print "Entered number only.....";
}
elsif( $get_mod_op == 1 ) {
print "Good odd number(${get_mod_op}): ${ip_no} ";
$finish = 1;
}
else {
print "Good even number(${get_mod_op}): ${ip_no} ";
$finish = 1;
}
}

Answer 3

Are you sure you want it to be interactive; doing that makes it much less useful in other scripts.
If you must, then put the testing code into a sub, then use the sub to validate $ARGV[0], and if that fails, go into a loop that requests input and runs the validation.
Check out the Perl IO::Prompt module.

Answer 4

my $val;
for (;;) {
print "Some prompt: ";
$val = <STDIN>;
chomp $val;
last if is_valid($val);
print "Bad input. Valid inputs are ...\n";
}