#!/usr/bin/perl  
use strict; 
use warnings;

my $entry;
my @a;  
do { 
   print"\n Press 1 to enter a File or 2 to count Total Combinations:  "; 
   $entry=<STDIN>; chomp ($entry); 
 if ($entry==1) {  
    print"\n\n    Enter File Name to count number of LINES (.txt):  "; 
    my $filename = <STDIN>; 
    chomp $filename;
    open my $fh, "<", $filename or die "Cannot open $filename.\n";
    $fh=~s/\s+$//g; # To remove white space & empty 
           # lines after end of each text file
    my $count = 0;
    while ( <$fh> ) {$count++;}  
    print"\n    Lines in File $filename: $count\n\n";
    push @a, $count;  
 
  } 
 
  } until ($entry==2);

my $product=1; 
   $product *= $_ foreach @a;
   print"\n\n Total Combinations: $product\n";
 
exit;

##</code><code>##

  
C:\Users\x\Desktop>c.pl

 Press 1 to enter a File or 2 to count Total Combinations:  1


    Enter File Name to count number of LINES (.txt):  s1.txt

    Lines in File s1.txt: 864


 Press 1 to enter a File or 2 to count Total Combinations:  1


    Enter File Name to count number of LINES (.txt):  s2.txt

    Lines in File s2.txt: 864


 Press 1 to enter a File or 2 to count Total Combinations:  1


    Enter File Name to count number of LINES (.txt):  s3.txt

    Lines in File s3.txt: 864


 Press 1 to enter a File or 2 to count Total Combinations:  2

 Total Combinations: 644972544

C:\Users\x\Desktop>