($a,$b,$c,$d)=map {eval(\$$_)} (1..4);}

You probably meant

     ... = map {eval "\$$_"} (1..4);
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i.e. you want to evaluate the strings '$1', etc., which you get by interpolating $_ into the double-quoted expression "\$$_".  In this case it would also run under strict.

That said, I agree with Corion that there are better ways to achieve the same...