Unless you're in a very tight loops, this is negligible. Of course, I think resolving a symbolic reference is more expensive than calling a sub ref in a hash:

use strict;
my $func_name = "blah";

$functions{ $func_name }->( ... );
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You can keep strict on, and Perl doesn't have to search the current symbol table to find an appropriate CV -- it's three or four ops shorter. (Somehow, I think your parser probably eats up more cycles.)