sub worker {
    my( $Q ) = shift:
    while( my $workItem = $Q->dequeue ) {
        ## Perform query
        ## Perform comparison
        ## Perform output/cleanup
    }
}

##</code><code>##

## in the main thread:
my $outputMutex : shared;
...
open OUTFILE, '>', ...

## In the worker threads
    ...
    {
        lock $outputMutex;
        print OUTFILE ...
    }