zmv

zsh has a zmv utility for batch-renaming files:

$ ls
10_test.txt 1_test.txt  2_test.txt  3_test.txt  4_test.txt  5_test.txt  6_test.txt  7_test.txt  8_test.txt  9_test.txt
$ autoload -U zmv
$ zmv '(*)_test.txt' 'test_$1.txt'
$ ls
test_1.txt  test_10.txt test_2.txt  test_3.txt  test_4.txt  test_5.txt  test_6.txt  test_7.txt  test_8.txt  test_9.txt

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