$Archive::Extract::PREFER_BIN = 1 is significantly faster.

$ time perl -Ilib t/import/Math-BigInt.t
ok 1
1..1

real    1m36.401s
user    0m26.460s
sys 0m38.575s

$ time perl -Ilib t/import/Math-BigInt.t
ok 1
1..1

real    1m9.946s
user    0m18.658s
sys 0m18.854s

For #62