Generally speaking, Expect is an effective tool to use when you are trying to automate a process that is highly interactive. Some uses would include automating an FTP session to download patches, or automating a telnet session to run reports from an ERP system.

Basically "headless" operation. ^-^

Where I work I use expect to download virus DAT files from McAfee's ftp site.

If you seek to interact with Telnet or FTP servers, you can accomplish pretty much the same functionality by using Net::FTP or Net::Telnet.

More esoteric interactions, such as yours I'm sure, would be better solved with Expect.pm or directly using the GnuPG Perl module as merlyn states.

Good Luck! ^-^

fongsaiyuk