my $section = '';
foreach (@m) {
  if (
    /^		#match the start of the line
      \s*	#match 0 or more whitespace characters grab as many as we can
      (		#start captureing
        [\w\s]*?	#match 0 or more word or whitespace, grab as _few_ as posible
      )		#end capture
      \s*	#match 0 or more whitespace characters
      :		#until we reach the a colon
    /x 		#x added for the comments
    && 		#if the match fails we don't bother checking $1
    $1) {	#check if we captured any thing if there was only whitespace before the colon we won't have captured any thing
    $section = $1;	#if we actualy found a section label save it
  }
  #$section should now be set to the last section label we found.
  if ($section eq '...') {
...
}