G'day xtpu,

Welcome to the monastery.

There are a number of FAQs (in perlfaq8 and perlfaq9) with information about passwords. The most relevant to your question would be "How do I ask the user for a password?"; although, the others may be of interest.

You can put lexical variables in an anonymous scope to make them private. In the following demo script, only the subroutines initialise_password() and retrieve_password() have access to the $password variable: even if you accidentally used $password somewhere else in your code, it would be a completely different variable.

The following code shows the techniques you might use to read the password once at startup, store it in a private variable and retrieve it as many times as you want.

#!/usr/bin/env perl

use strict;
use warnings;

{
    my $password;

    sub retrieve_password {
        return $password if defined $password;
        die 'Password not defined';
    }

    sub initialise_password {
        return if defined $password;

        use Term::ReadKey;
        print 'Enter password: ';
        ReadMode('noecho');
        $password = ReadLine(0);
        print "\n";
        ReadMode('restore');
        return;
    }
} 

start();
test();

sub start {
    initialise_password();
}

sub test {
    print 'Testing: ', retrieve_password(), "\n";
}
[download]

Sample run:

Enter password: 
Testing: some_password
[download]

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