Um, '+' means at least one (and you don't need the box): ! /^\s*$/ Anyway, it's even easier just to check for a non-space: /\S/ But, as long as we're at it, why not accept only well-formed lines:

if ( /^(\w+)\s+([\d.]+)/ ) {

   ($names[$l],$versions[$l])=($1,$2);
   ++$l;

else { . . .
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  p