#include <iostream>
#include <string>

using namespace std;

int main () {
  string user_input;
  cout << "Please enter a five digit integer: ";
  cin >> user_input;
  for ( size_t ix = 0; ix != user_input.size(); ++ix ) {
    for ( size_t count = 0; count <= ix; ++count )
      cout << user_input.at(ix);
    cout << endl;
  }
  return 0;
}
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Oh, you your instructor wanted Perl? This is where you'll have to learn to adapt. ;) Update: Actually Perl can adapt for you:

#!/usr/bin/env perl

use strict;
use warnings;

use Inline CPP => <<'EOC';
#include <iostream>
#include <string>

void doit () {
  std::string user_input;
  std::cout << "Please enter a five digit integer: ";
  std::cin >> user_input;
  for ( size_t ix = 0; ix != user_input.size(); ++ix ) {
    for ( size_t count = 0; count <= ix; ++count )
      std::cout << user_input.at(ix);
    std::cout << std::endl;
  }
}
EOC

doit;
[download]

After you turn in a serious solution, try this just for fun. :)