Add ^^ as a logical boolean XOR expression

[DartBot]

This issue was originally filed by domi...@google.com

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The binary expressions include &, | and ^ but the logical boolean expressions only have && and ||. Adding ^^ for XOR will be consistent (and it will make my code shorter).

[rakudrama]

&& and || are short-circuit because 'and' and 'or' 'stick' at false and true respectively.
^^ has no such property - both operands must always be evaluated.
This makes ^^ just a synonym for !=

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Removed Type-Defect label.
Added Type-Enhancement, Area-Language, Triaged labels.

[gbracha]

Set owner to @gbracha.
Added Accepted label.

[anders-sandholm]

We suggest using the mostly equivalent !=

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Added WontFix label.

[ThinkDigitalSoftware]

&& and || are short-circuit because 'and' and 'or' 'stick' at false and true respectively.
^^ has no such property - both operands must always be evaluated.
This makes ^^ just a synonym for !=

Removed Type-Defect label.
Added Type-Enhancement, Area-Language, Triaged labels.

oh! Thank you!!! that's what I need!!!! Trying to make sure both of my operands are not the same