Don't forget that our friend next will work in a while loop. Combining some of these answers gets you the technique I prefer: 
while (<FILE>) {
    next if /^#/;    # skip lines starting with comments
    next unless /\S/;
    # do something with a real line here
}

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This allows you to use a normal loop construct (makes sense to me) and short-circuit it at the beginning if certain conditions are met. It makes cleaner code than a lot of if-elsif statements.

In reply to Re: How do I remove blank lines from text files? by chromatic
in thread How do I remove blank lines from text files? by dumpest

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