Note that for($x..$y) is optimized to be lazy but that isn't true for for(eval"$x..$y"). For example:

 $ perl
$x=1<<30;
for(1..$x){last;}
warn "first";
for(eval "1..$x"){last;}
warn "second";
__END__
first at - line 3.
core dumped
[download]

The for(1..$x) very quickly tries $_=1 and then exits the loop. The for(eval "1..$x") doesn't even run because it tries to build the entire "1..1<<30" list in memory before it can get started and it runs out of memory and dumps core before then.

Just something to keep in mind.