:   '''[thread]::send''' ?'''-async'''? ?'''-head'''? ''id script'' ?''varname''?

Sends a message to the [thread] described by ''id''. The message consists of a ''script'' that will be [eval]uated in the [global scope] of the master interpreter of that thread. Unless '''-async''' is specified, will wait for the script to be evaluated before allowing the current thread to continue.

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''[[TODO: document the '''-head''' and ''varname'' bits of this command.]]''

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