bash-2.05$ perl -ple "@f=split; for (@f[1..4]) { $_=1000 if $_>1000; } $_=join(' ',@f)" TEST 
Can't modify constant item in scalar assignment at -e line 1, near "1000 if"
Execution of -e aborted due to compilation errors.

bash-2.05$ perl -lape "for(@F[1..4]){ $_=1000 if $_>1000 } $_=qq{@F}" TEST 
Can't modify constant item in scalar assignment at -e line 1, near "1000 if"
Execution of -e aborted due to compilation errors.