The answer can be found in the manpage to select:

"Second, references to variables related to output will refer to this output channel".

See also the example directly below that sentence.

Since you define the format for STDOUT (before the select() call) no format is defined for FILE. Solution: Move the format definition after the select()

UPDATE: Since no one else seemed willing to risk brain damage to answer your second question I had to do it myself: Setting $- to 0 will force a new page on the next write. This is described in write

In reply to Re: Writing to a file using Formats by jethro
in thread Writing to a file using Formats by biohisham

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