I don't see a need for a dispatch table here. I thought for a while that a comma operator might be a usefull thing, but in the end I suspect that the following is fairly tidy and efficient:

my $msg = "Status has changed" 
    if $bbstatus ne $last_bbstatus; 
$msg = "Last send too old" 
    if ! length $msg and ($now - $last_send_time) > $min_frequency;
$msg = "Forced send requested" 
    if ! length $msg and defined($OPTS::opts{f});

$send_flag = length $msg;
$msg ||= "No changes";
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BTW, if you are interested in seeing an almost dispatch table in use take a look at Ook interpreter. %xlate could be used as is as a dispatch table, but instead it is used to 'compile' the source to generate 'machine code' in @code