unshift would be bad. That puts "./" at the start of the search list, which means standard module names could be overridden by placing bogus ones in the CWD.

push @INC,"./";
[download]

Better, but it isn't going to affect use statements, since those are evaluated at compile time. So,

use lib "./";
[download]

is even better. But best is:

use lib /some/absolute/path/that/you/control;
[download]

Update: use lib "./" is worse than unshift @INC,"./" because it also prepends "./" to the search path, but does so at compile time, where it can affect other use statements.