Well, you should be aware of the fact that the next from within the eval jumps to the end of an enclosing loop, which might be a little bit surprising. Example:

my $var = 5;
{
  eval {$var = 3; next};
  $var = 4;
}
print $var; # 3 !!
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The block after eval does not count as a loop block (same as do), so the loop commands next, redo and last work on the outer block. To make the eval block a loop block (so that you can redo it e.g.) double the braces like this:

eval {{
  $i++;
  redo unless do_sth($i);
}}
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-- Hofmator