This just makes things unnecessarily more complicated, scain. The original version is absolutely equivalent to yours and shorter to write - thus easier to understand. $string =~ s/^\s*(.*?)\s*$/$1/;

Some further explanation: The starting \s* eats up all whitespaces (because its greedy). Then (.*?) starts capturing and the first character must be \S (or the end of the string for something matching /^\s*$/). Due to its non-greediness the (.*?) advances slowly one character at a time, always trying to match afterwards the rest of the pattern (\s*$) and backtracks if not successful. So all trailing whitespaces are for sure eaten up by the greedy \s* at the end of the pattern leaving a \S as the last character in the capturing brackets.

The solution with two replaces given by many other monks is preferable as it

• is quicker
• doesn't get caught on embedded newlines (as . matches by default everything but a newline) - if you only want to remove space at the beginning and end of the string
• is easily adaptable to remove all leading and trailing whitespaces on a slurped file:

  $file =~ s/^\s+//mg;
  $file =~ s/\s+$//mg;
  [download]

-- Hofmator