It does make more sense when you read it out loud, but since there's no semantic difference, it sometimes helps to place immutables as the first operand since then you'll get a compiler error out of the simple typo:

unless ($foo = 4) {
   ... argle blougat blopf ...
}
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when it looks like this:

unless (4 = $foo) {
   ... womble ...
}
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