You print stuff to a file handle. I think you want something like this:

print AT_LIST qx'AT $bch';
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I don't know much about the AT command, so I'm assuming it's similar to the Unix at command.

I've removed the comma between AT and $bch as it looks to me like that's completely unnecessary - I could be wrong there. Also, don't you need to give AT at time?

Note, also, that this will return the output from the AT call - not the output of the command that AT runs.