Am I missing somethig? I assume that '$returnstring' is what you want back. In which case it should not be in the argument list. The code to do this is simply...

sub getString {
  my ($a,$b) = $@_;
  return "$a$b";  # OR  return $a.$b;
}

#usage...
my ($str1, $str2); 
my $returnstring = &getString($str1,$str2);
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