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use strict;
use warnings;
...
  unshift @from, shift @to for @to;
  }
}

               Rate unshift shift      push pop   unshift pop    push 
+shift
unshift shift 129/s            --           -0%           -4%         
+  -6%
push pop      129/s            0%            --           -3%         
+  -6%
unshift pop   134/s            4%            3%            --         
+  -2%
push shift    137/s            6%            6%            2%         
+   --