grandagent,
You said "but it only give me the first user in the hash" when what you should have said is "it only produces output for user rmdb_dbo". That's because your if condition is only displaying output for that user. Try this to debug:

for my $connection (keys %h) {
    print "Looking at connection '$connection'\n";
    for my $userid (keys %{$h{$connection}}) {
        print "\tLooking at userid '$userid'\n";
        @a_ref = @{$h{$connection}{$userid}};
        if(lc($userid) eq "rmdb_dbo") {
            print @a_ref, if ( $a_ref[1] =~ m/update\s*[table\s*]rmdb_
+dbo./i );
        }
        else {
            print "Not checking '@a_ref' because user is not 'rmdb_dbo
+'\n";
        }
    }
}
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