title: how to make combination between the fields in 2 columns?
body: <p>There are always some data including two associating groups(columns). And each column may include several situation seperated by some symbols (the input is common example in biology data). How to split them and keep all of the pairs between columns?</p>
  <p>input:</p>
  <pre><code>$cat input.txt
  PEX10       TPRG1L
  SKI         MORN1;RER1
  MORN1;RER1  TTC34
  MORN1;RER1  TP73;WRAP73
  BEST4       TCTEX1D4;PLK3;BTBD19
  </code></pre>
  <p>output:</p>
  <pre><code>PEX10       TPRG1L
  SKI         MORN1
  SKI         RER1
  MORN1       TTC34
  RER1        TTC34
  MORN1       TP73
  MORN1       WRAP73
  RER1        TP73
  RER1        WRAP73
  BEST4       TCTEX1D4
  BEST4       PLK3
  BEST4       BTBD19
  </code></pre>