If the variables are declared already above your loop, then you can do it via string eval. E.g.

#!/usr/bin/perl

use strict;
use warnings;

my ($blah, $boo, $hoo);  # DECLARED HERE

my %data = ( "blah"=>1, "boo"=>2, "hoo"=>3 );

# assign each key to a variable of the same name
foreach (keys %data) {
  eval " \$$_ = \$data{$_} ";
} # end-foreach

print $blah;

exit;
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Replace is still probably a better long run strategy.