# style: what i like (my latest first two attempts)
perl -e"printf('%4s: %s',++$a,$_)while(<>)" file
perl -e"printf'%4s: %s',++$a,$_ while<>" file

# then i did a lot of searching, and ran accross clemburg's solution
# (which was 'broken' like the craft version, see end)
perl -pe "s/^/++$i.' 'x4/e" file

# then i remembered -p and broke it down to
### which is by far my favorite (the one i use)
perl -pe "printf'%4s: ',++$a" file


# style: merlyn (as featured in WebTechniques)
perl -pe"printf'%6s ','='.++$a.'='" file

# or more acurately
perl -pe"printf'%-6s ','='.++$a.'='" file

# or most accurately (since his output looks like'        =2=     code')
perl -pe"printf'%8s%-8s ','','='.++$a.'='" file


# style: [craft] (craft doesn't handle 3digits well)
# you can always change the 2 into 3 to handle 3 digit nums
perl -pe"printf'%-2s: ',++$a" file