I think davido's reply is on the right track. To put that in other terms, consider the problem as follows:

• Starting with the call to do_command(), you set $nick to be the value provided by $event->{nick}, but you don't test to see if this value is "defined" or non-empty
• You pass $nick to do_help(), and this sub doesn't check whether $nick is defined either -- all it does is...
• Pass the value on to is_master(), at which point it is used for the first time in a conditional statement, where "strict" will complain that it's bad to use "eq" when one value is undefined.

So the question is, what calls "do_command()", and how will you figure out why it's providing an incomplete set of data.

As for the other things within do_command and do_help that seem to be using $nick without any trouble, you should be aware that it's possible, grammatical, and no problem under "use strict", for a hash key to be an undefined value (although if you "use warnings" or include the "-w" flag, you will get run-time warnings about assigning to or referencing a hash element using an "undef" value as the hash key -- e.g. try the following test script, with and without the "-w" flag (or with and without "use warnings;"):

use strict;
my %hash;
my $key = undef;
$hash{$key} = 3;
print "A hash element with value $hash{$key} is stored with key=$key\n
+";
[download]

Obviously, if you repeatedly use an undef or empty hash key to store different values into a hash, subsequent values will replace previous ones.