2:05 >type nums.txt 1 2 3 4 2:05 >perl -nE "$sum += $_; END { say $sum }" nums.txt 10 2:06 >perl -nwE "$sum += $_; END { say $sum }" nums.txt 10 2:06 >perl -nE "$sum += $_; END { say $sun }" nums.txt 2:06 >perl -nwE "$sum += $_; END { say $sun }" nums.txt Name "main::sum" used only once: possible typo at -e line 1. Name "main::sun" used only once: possible typo at -e line 1. Use of uninitialized value $sun in say at -e line 1, <> line 4. 2:06 >