Personally, I don't see any need to improve on the old standard: 
s/^\s+//;
s/\s+$//;

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update: After seeing thinker's reply I realized I might have misunderstood the question. If, like he suggests, you mean to remove leading and trailing whitespace from each line of a multi-line string, then I'd change the second line above to: 
s/\s*\n\s*/\n/g;

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In reply to Re: trim leading & trailing whitespace by graff
in thread trim leading & trailing whitespace by ady

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