Update: 'tis broken. See sauoq's reply.

Do you really just want the first word, even if there are several before the colon? In that case, 21.

#        1         2
#23456789012345678901
map/^([^:\s]+)/,@list
[download]

If you want to allow optional whitespace at the start of a line, 24.

#        1         2
#23456789012345678901234
map/^\s*([^:\s]+)/,@list
[download]

Makeshifts last the longest.