If you're a beginner (and even if you're not), it's almost always a good idea to  usewarnings; and  usestrict; in all your scripts. Take a look at the warnings (not errors) below and try to fix them, then come back for more enlightenment.

c:\@Work\Perl\monks\Sellerzzz>type text
line 1
second line
line the third

c:\@Work\Perl\monks\Sellerzzz>perl -e
"use warnings;
 use strict;
 ;;
 my @sig;
 ;;
 print \"Enter file name: \n\";
 my $file = <STDIN>;
 chomp $file;
 ;;
 open (INPUT, $file) || die(\"Could not find $file\");
 while (my $line = <INPUT>)
 {
      push @sig, <INPUT>, $_;
 for (my $i; ($i<=scalar @sig); $i++){
     for (my $j=($i+1); ($j<=scalar@sig); $j++){
         print \"@sig[$j]\n\";
     }
 }
 close;
 }
"
Scalar value @sig[$j] better written as $sig[$j] at -e line 1.
Enter file name:
text
Use of uninitialized value $i in numeric le (<=) at -e line 1, <INPUT>
+ line 3.
Use of uninitialized value $i in addition (+) at -e line 1, <INPUT> li
+ne 3.
line the third

Use of uninitialized value $sig[2] in join or string at -e line 1, <IN
+PUT> line 3.

Use of uninitialized value in join or string at -e line 1, <INPUT> lin
+e 3.

Use of uninitialized value $sig[2] in join or string at -e line 1, <IN
+PUT> line 3.

Use of uninitialized value in join or string at -e line 1, <INPUT> lin
+e 3.

Use of uninitialized value in join or string at -e line 1, <INPUT> lin
+e 3.
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I have taken out the use of Text::CSV_XS in the example code since it adds nothing to the point I want to make. BTW: congratulations on the use of a nice Short, Self Contained, Correct (Compilable), Example; pursue the problems it highlights and you will be well on your way to wisdom.