You don't show us a script, but this is what use strict; does - it forces you to predeclare all the variable names you intend to use. This is a good thing because it finds typos like the following:

use strict;

my $variable_with_a_very_long_name = 1;
print "The value is >>$varaible_with_a_very_long_name<<";
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As your script seems to work with use strict; commented out, likely your script contains no typos and all you need is to predeclare your global variables:

# for global variables:
use vars qw(@users $account);
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If a variable isn't used in global scope, you want to declare it lexically within the block it is used in via the my keyword:

for $user (@users) {
    $message = "Hello $user!";
    ...
};

# should become

for my $user (@users) {
    my $message = "Hello $user!";
};
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