#!/usr/bin/perl -w

$template_file = "test.pl";
$template = "old value";
print "Before call: $template \n";

$cnt = read_template(\$template_file, \$template);

print "$cnt lines read \n";
print "after call: $template \n";


sub read_template {

  my $file_name = ${shift()};
  my $lines_in  = ${shift()};
  my $line_cnt  = 0;

  if (!open (INPUT, "< $file_name")) {
    die "Can't open $file_name as input.";
  } else {
    while (<INPUT>) {
      $line_cnt++;
      $lines_in .= $_;
    }
    close (INPUT);
  }
  return($line_cnt);
}

##</code><code>##

Before call: old value 
29 lines read 
after call: old value