in reply to Faster way to regex this
Have you tried using a character class?
$dir =~ s/([\[\]{}~*?])/\\$1/g; [download]
A look-ahead might be faster, but this still doesn't address the question of \ (backslash) handling raised by Corion below.
c:\@Work\Perl\monks>perl -wMstrict -le "my $s = 'foo\bar\[baz[x]x{x}x~x*x?x[]{}~*?'; print qq{'$s'}; ;; $s =~ s{ (?= [][{}~*?]) }{\\}xmsg; print qq{'$s'}; " 'foo\bar\[baz[x]x{x}x~x*x?x[]{}~*?' 'foo\bar\\[baz\[x\]x\{x\}x\~x\*x\?x\[\]\{\}\~\*\?' [download]