{
    my $Entry =
      sub {
          my ($self,$textvar) = @_;
          return $self
            ->Entry(-width => 3,-borderwidth => 4, -textvariable => $textvar)
              ->pack(-side => 'left', -expand => 1,-padx=>5);
      };

    # ...

    $fr2a->$Entry(\$size_help);
}

##</code><code>##

$fr2a->Entry(-width => 3,-borderwidth => 4, -textvariable => \$size_help)->pack(-side => 'left', -expand => 1,-padx=>5);