#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

for my $string (
    '--server api.blr-ocp1.lab.rbbn.com --username mgore --password abc123',
    '--server api.blr-ocp1.lab.rbbn.com --token kfjshdssahdvkbvjkbj'
) {
    if ($string
        =~ /^--server\s+(?<server>\S+)\s+
            (?:--username\s+(?<username>\S+)\s+--password\s+(?<password>\S+)
             |--token\s+(?<token>\S+))/x
    ) {
        say 'Server: ', ${^CAPTURE}{server};
        if (exists ${^CAPTURE}{token}) {
            say 'Token: ', ${^CAPTURE}{token};
        } else {
            say 'Username: ', ${^CAPTURE}{username};
            say 'Password: ', ${^CAPTURE}{password};
        }
    } else {
        say 'No match';
    }
}