Quoth the docs for print:

Note that if you're storing FILEHANDLEs in an array, or if you're using any other expression more complex than a scalar variable to retrieve it, you will have to use a block returning the filehandle value instead:

print { $files[$i] } "stuff\n";
print { $OK ? STDOUT : STDERR } "stuff\n";
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Update: Duur, read not write. You want readline (readline( $hash{handle} )). Ignore that first part.