I'm not convinced that the use of |...| to mean abs(...) doesn't break the existing grammar or introduces ugly whitespace dependency:

1+|a+b|+c+d|+1
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can be naively parsed as

1+abs(a+(b|+c)+d)+1
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or as

1+abs(a+b)+c+(d|+1)
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because the ugly unary + is allowed, which breaks lots of things. Of course, introducing another slew of operator precedence could fix this, but I imagine it creates more confusion than the "clearer" syntax removes.