Here's my shot (37 chars): 
map{/([^:]*?)(\s*\n|\s*:)/&&$1}@list;

# silly me ... distributive property! update: 34 chars:

map{/([^:]*?)\s*(\n|:)/&&$1}@list;

[download]
I tested it with the following data and it seemed to work correctly: 
__DATA__
123 : oain:b:okfbd

456
foo bar    : df a dsaf asdf
111 :

[download]
It doesn't work when the input line contains only whitespace, but it does work for blank (other than the \n) lines. It returns empty string when the colon is the first non-whitespace. I don't know if this is correct behavior or not, though! This is my first golf attempt, so I may have missed some regex shortening tricks.

Update: Here's a slightly different approach that's the same 34 chars, although it behaves differently. This one does ignore lines of complete whitespace. It still gives empty string when a colon is the first non-whitespace in the line. 

map{(split/\s*(:|\n|$)/)[0]}@list;

[download]

blokhead

In reply to Re: golf anyone? (taking first field) by blokhead
in thread golf anyone? (taking first field) by John M. Dlugosz

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