Error1 is: ...

Ok, so what's the code that produces the error? I don't see any  eq operator ("string eq") in the OPed code, nor a  $concept1 scalar. (Update: A small point: a "warning" (see warnings, which you are wise to use, as you seem to be doing) is not an error, but merits your attention nonetheless.)

Update: Rats. Many small changes to added update sentence in preceding paragraph just to get it to make sense!

# UMLS::Similarity::lch.pm
#
# Module implementing the semantic relatedness measure described 
# by Leacock and Chodorow (1998).
#
<code>


sub getRelatedness
{
    my $self = shift;

    return undef if(!defined $self || !ref $self);

    my $concept1 = shift;
    my $concept2 = shift;

        #  get the interfaceg
    my $interface = $self->{'interface'};

    #  find the length of the shortest path
    #  if concept 1 and 2 are the same just return 1
    my $length = 0;
    if($concept1 eq $concept2) { $length = 1; }
    else { $length = $interface->findShortestPathLength($concept1, $co
+ncept2); }

    #  get the depth of the taxonomy
    my $depth = $interface->depth();
    
    #  if the length of hte path is less than zero return -1
    if($length < 0) { return -1; }

    #  calculate lch
    my $score = -1 * log ($length / (2 * $depth));
    
    return $score;

}


=
[download]

this subroutine in code is by default present in umls::similarity package. Where our $t1 is passes as $concept1 and $t2 is passed as $concept 2.So I dont think there is anything wrong in this code.What am I thinking is maybe $t1 is not able to get value as string the way it should be.Well I am beginner so I dont have much knowledge so plz help me

I have never used nor even seen the UMLS::Similarity::lch module before and, after a brief perusal, have only the vaguest idea of what it is supposed to do. However, total ignorance should never prevent a righteous monk from offering an opinion! So...

my $cu1 = $umls->getConceptList($t1); #calling function from umls::sim
+ilarity #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);
[download]

If the value (which should be an array reference) returned to  $cu1 by the call to the  getConceptList() method in the
    my $cu1 = $umls->getConceptList($t1); #calling function from umls::similarity #ERRRO 1 as mentioned
statement is undefined or is a reference to an empty array, the value assigned to  $cui1 by the pop in
     my $cui1 =pop @{$cu1};
will be undefined, as your comment to the
     print $cui1;    # ****ERROR2 unintialized $cui1
statement suggests.

Because an undefined  $cui1 will become an undefined  $concept1 within the call to the  getRelatedness() method, you will get a warning like "Use of uninitialized value $concept1 in string eq at UMLS/Similarity/lch.pm ... at the line number associated with the
    if($concept1 eq $concept2) { $length = 1; }
statement in getRelatedness().

So your first step is to determine whether  $cu1 is undefined or a reference to an empty array. I would do this with a Data::Dumper print debugging statement after the method call:
    my $cu1 = $umls->getConceptList($t1);
    print Dumper $cu1;
Once you know the value of $cu1, you can figure out from the documentation (or the source) of  getConceptList() why it has this value given that you know the value $t1.

I hope this helps. It seems you've already gone quite a way through the steps I've outlined, but maybe this will help clarify things a bit.

---

Give a man a fish:  <%-{-{-{-<