Then you can probably get away with grabbing the source, changing the package declaration to MyTieIxHash or something, and uploading to MyTieIxHash.pm, and then use tie %hash, 'MyTieIxHash';. YMMV.

Update: Ah, I didn't see that you can create directories. In that case, create "Tie" directory, put "IxHash.pm" in it, add "use lib '.'" to your script, and you should be good to go.