If you want to change every line in some files then

perl -pe's/^([[:alpha:]]+)/ uc $1 /e' -i.bak <file list>
[download]

you can use a condition to change just some lines

perl -pe's/^([[:alpha:]]+)/ uc $1 /e if condition' -i.bak <file list>
[download]

The original file is saved with a extention of .bak