$bleh="-a 123 -b 456 -c 789 -d 333"; 
$bleh=~s/-([bc])/-:$1/g;
print $bleh;
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I think you want

        s/-([bc])/-:$1/g
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You can find bits and not replace them using lookahead and lookbehind assertions:

$bleh =~ s/(?<=-)(?=b|c)/:/g;
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For more details see perlman:perlre or Super Search for "lookahead assertions" in the text +/- "tachyon" as author as I know I have written a summary on this a while back.

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

1. Many options, but basically you must account for the difference between substrings and stand-alone strings, and this appears to be whitespace in your example data, hence something like:
   s/(?<=\s)-([bc]\s)/-:$1/g;
2. You can stop split from continuing using the 3rd argument:
   split( '\s', 'a b c', 2);
   though if there may be leading whitespace before the 'a' you'd better use the special case of splitting on a single space, which will discard any leading whitespace:
   split( ' ', '  a b c', 2);
   

--
I'd like to be able to assign to an luser

s/-([bc])/-:$1/g; actually doesn't look for the whole string at all--[bc] is a character class, not a literal string.

This means that your regex translates to

• Find a dash ("-")
• Followed by either a "b" or a "c" (save this character in $1)

when you wanted that second line to read "the string 'bc' (save this string in $1)".

The easy solution is to take those brackets out:

s/-(bc)/-:$1/g;

and for what I'm guessing is the next step (multiple strings that could match), you can use

s/-(foo|bar|bc|whatever)/-:$1/g;

But in fact you might be better off with tachyon's suggestion:

s/(?<=-)(?=foo|bar|baz)/:/g; #assuming you have 5.005 or better

The longer but more rewarding solution is to take another couple of trips through perlre when you have a moment--regexen are not the fastest thing in the world to pick up (for us mere mortals, anyway) but they reward study very nicely. :-)

Your other question just needs the last argument to split:

($first, $second) = split ' ', "a  b c", 2;
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and you're all set. Good luck!

Update: fixed boneheaded mistake in split (thanks, Hofmator!)




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If God had meant us to fly, he would *never* have given us the railroads.
    --Michael Flanders