Seems like an overkill, but if you really want ALL your variables available for the user, that essentially is equivalent to making a copy of the entire symbol table, and handing it over the the user to mess with. The only way to reconstruct it is to save everything. That is essentially a fork or a thread, so this works 
use threads;

my $x=1;

my $threads = threads->new(sub {eval '(++$x)+1'});
print "The value of \$x before eval is $x\n";
my $val = $threads->join();
print "The eval returned $val\n";
print "The value of \$x after eval is $x\n";

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giving the result 
The value of $x before eval is 1
The eval returned 3
The value of $x after eval is 1

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It seems like overkill, but then, you asked for it. Less expensive might be to copy that part of the symbol table that you want shared with the user, and restore it after they are done.

In reply to Re^3: eval something using private copy of variables by b4swine
in thread eval something using private copy of variables by gboole

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