Granted it may be a relic of your sample simplification, but in this case I might had factored out the common bits into a helper that looks up the exact arguments from a hash instead (and then sets up methods for each task based on the contents of the hash). 

my %helper_args = (
  Task1 => [ qw(ARG1 ARG2 ARG3) ],
  Task2 => [ qw(ARG6 ARG2 ARG1 ARG5) ],
  ## ...
);

for my $task ( keys %helper_args ) {
  *{"Do$task"} = sub { $_[0]->_common_runner( $task, @_[1..$#_] ) };
}

sub _common_runner {
  my $self = shift;
  my $task = shift; ## "Task1", "Task2", ...
  my @rest = @_;

  if( !$self->TaskIsDone() and (my( $setup ) = $self->can( "Setup$task
+" )) ) {
    $self->$setup();
  }

  my @args = @{ $helper_args{ $task } || [] };

  $self->CommonTask( @args, @rest );
}

[download]

Alternately create a common base class and then have that base class' CommonTask calls methods on itself (with the base class' implementations being noops / stubs); in other words the Gang Of Four "Template Method Pattern".

Update: Oh, and to actually answer your question no that's not a totally bletcherous solution and that is one of the "accepted" usages of prototypes (to get new keyword-like syntax).

The cake is a lie.
The cake is a lie.
The cake is a lie.

In reply to Re: Caveats when using anonymous subs as subroutine arguments by Fletch
in thread Caveats when using anonymous subs as subroutine arguments by Glav

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.