# foreach (@Dirs)
   # foreach (@Dirs)
   # for ( 0 .. $#AbsDirs )
      # for ( 0 .. $#files )
   # for ( 0 .. $#AbsFiles )
      # if( $AbsFiles[$c] =~ /R2_001.fastq$/ )
         # while(<INPUT1>)
            # if( @readbuffer == 4 )
   # for ( 0 .. $#AbsFiles )
      # if( $AbsFiles[$d] =~ /R1_001.fastq$/ )
         # while(<INPUT2>)
            # if( @readbuffer == 4 )
               # if( exists( $input1{$key2} ) )
               # else