I keep forgetting to put Exporter in @ISA
I don't really like to inherit from another module just to use one or two subs. Instead I write use Exporter qw(import);.
And when (interactively) querying a database, the client has to remind me over and over again that 'cd' and 'ls' aren't valid commands.
This happens to me all the time as well. When I use the mysql prompt and enter ls<return> I see my mistake, and then press Ctrl+C to abort the command. But of course Ctrl+C actually exists the client...