sub read_file {
          my $file = shift;
          -f $file || return undef;  #file doesn't exist!

          #Continue reading file...
      }

      #and later...

      if ( my @data = read_file($filename) ){

          # if $filename doesn't exist,
          # @data will be (undef),
          # but I'll still be in here!

          process(@data);
      }
      else{

          # This is my error handling code.
          # I probably want to be in here
          # if $filname doesn't exist.

          die "$filename not found";
      }