Good work. Two comments:

        if(scalar(@directories)>=4){
            @part= @directories[0..3];
        }    
        
        #Take as many as possible when <4 elements in the array
        elsif(scalar(@directories)<4){
            @part = @directories [0..scalar(@directories)];

        }
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This is overkill, since you can reference non-existing array elements in perl without problems. So the following is equivalent:

       @part= @directories[0..3];
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The line

if ($pid == -1) {
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should be

if (not $pid) {
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because fork returns undef on failure, unlike the C library fork which returns -1