…this is not very efficient in Perl…

You may refer to some disappointing benchmark as this:

              Rate goto_recur  recursive tail_recur    looping
goto_recur  3437/s         --       -59%       -60%       -90%
recursive   8472/s       147%         --        -1%       -76%
tail_recur  8569/s       149%         1%         --       -76%
looping    35417/s       931%       318%       313%         --
[download]

where the benchmark is that of swampyankee above, adding ikegami's tail_recur and a derived version of that using your goto recipe:

sub _goto_recur {
   my ($x, $y) = @_;

   if ($x <= 1) {
      return $y;
   } else {
      @_ = ($x - 1, $x * $y);
      goto &_goto_recur;
   }
}

sub goto_recur {
   my ($x) = @_;
   return _goto_recur($x, 1);
}
[download]

Then I was surprised that throwing out all lexicals and directly messing with @_ yields more pleasing results:

sub _goto_recur {
   if ($_[0] <= 1) {
      return $_[1];
   } else {
      $_[1] *= $_[0];
      --$_[0];
      goto &_goto_recur;
   }
}

sub goto_recur {
   my ($x, $y) = (shift, 1);
   # We can't plug the constant 1 directly into $_[1]
   # since we want to change that (alias!)
   return _goto_recur($x, $y);
}
[download]

Gives on my machine:

              Rate  recursive tail_recur goto_recur    looping
recursive   8456/s         --        -1%        -9%       -77%
tail_recur  8519/s         1%         --        -8%       -76%
goto_recur  9278/s        10%         9%         --       -74%
looping    36011/s       326%       323%       288%         --
[download]

Of course that code does not look very desirable from a maintainers point of view.

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