My second edition camel book shows how to do it. The critical points are: 1) put the output of the format statement into a variable, 2) eval that variable. Here is a piece of demonstration code. I have tried to make it readable, it is surely not the most compact version possible.

$data = qw( aaa bbb ccc );
$fields = scalar @data;
$data_fields = "";
map $data_fields .= '"' . $_ . '"', @data;
$format = "format STDOUT = \n"
        . "@<<< " x $fields . "\n"
        . $data_fields . "\n";
        . ".\n";
eval $format;
write;
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HTH, --traveler