I've had no end of trouble with at on NT (et al) so I simply create a bat file using pl2bat and use the task scheduler if available.
in reply to Schedule Win32 Perl Scripts with AT
On windows advanced server (where I do most of my work) I can set up the program to run as any user I like from within the task scheduler so can avoid having to put my credentials into the Perl source if it is required to have them.
I don't recall 98 (haven't used it in ages) but task scheduler is also available on WinMe for those unfortunate enough to own it. If you do use WinMe then you won't have the credential possibilities for obvious reasons.
Just an alternate solution :)