picard:~ [13:47:28]$ perl -le '$x[5]=5; $_*=10 for @x; print "@x"'
0 0 0 0 0 50
picard:~ [13:47:32]$ perl -le '$x[5]=5; $_*=10 for grep 1, @x; print "@x"'
Modification of a read-only value attempted at -e line 1.
picard:~ [13:47:36]$ perl -le '@x=0..5; $_*=10 for grep 1, @x; print "@x"'
0 10 20 30 40 50