******CODE**************

for(my $i=0;$i<$n_size;$i++){
      my  @w= split(/,/ , $new[$i]);
     
      $w[0]=~s/\'//;  #pre-process to remove ' from text 
      $w[0]=~s/\'//;    as @w='word1' 'word2'
      $w[1]=~s/\'//;  
      $w[1]=~s/\'//; 
      
      
      my $t1 = "$w[0]";  #$w[0]=word1  without single quotes
      my $t2 = "$w[1]";  #$w[1]=word2
     
      print $t1,$t2,"__________";   #working
      
     my $cu1 = $umls->getConceptList($t1); #calling function from umls::similarity #ERRRO 1 as mentioned
      my $cui1 =pop @{$cu1};
      my $cu2 = $umls->getConceptList($t2);***error
      my $cui2 = pop @{$cu2};
      print $cui1;    # ****ERROR2 unintialized $cui1
      my $lvalue = $lch->getRelatedness($cui1, $cui2); 
      my $value = $path->getRelatedness($cui1, $cui2);