4. It's nowhere near as easy for the caller to dynamically construct a bitmask as it is to dynamically construct a list of booleans. You will spend a lot of time doing things like

my $param = 0;
$param |= FOO if $foo > 0;
$param |= BAR if $bar != 1;
$param |= BAZ if $baz > $foo;
quux($param);
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where you would otherwise just write quux($foo > 0, $bar != 1, $baz > $foo); Ok, it might work (I didn't test, might need an extra dozen parens) to say something like quux( ($foo > 0 && FOO) | ($bar != 1 && BAR) | ($baz > $foo && BAZ) ); but I don't think I need to comment on that.

Makeshifts last the longest.