DB<33> sub trim { $_[1] //= qr/\s/; $_[0] =~ s/^[$_[1]]+|[$_[1]]+$//g }

  DB<34> $a = $b = "  \n . aaa . \n  "

  DB<35> trim $a

  DB<36> trim $b, " "

  DB<37> x $a,$b
0  '. aaa .'
1  '
 . aaa .
'
  DB<38>