Something to be mindful of is the possibility of no corresponding entry in the dispatch table, either by accident (ie, a typo), negligence, or something more sinister.

A quick fix could be as simple as checking that get_branch_function's returned something true...

# get appropriate function
my $function = get_branch_function( $query )
  or die "Holy Missing Function, Batman!";
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... while the more paranoid among us could then use ref or something to check it was something that could actually be run with $function->().

    --k.