For this example, at least, I don't think I'd bother with a regex. Instead, I'd split the string up into individual characters, process each character, and join the results back into a string: 
my $word = 'layer';
my $new_word = join '', map { "[$_]" } split '', $word;

# Or, if I want to be more explicit about the process:
# my @raw_chars = split '', $word;
# my @cooked_chars = map { "[$_]" } @raw_chars;
# my $new_word = join '', @cooked_chars;

[download]

Edit: As pointed out in replies, the spec was to only bracket characters in the range a-zA-Z, not all characters. This can be fixed with a minor adjustment to the map. Change it to map { $_ =~ /[a-zA-Z]/ ? "[$_]" : $_ } and you get the result: 

$ perl -E '$word = "layer123 $-.% foo"; $new_word = join "", map { $_ 
+=~ /[a-zA-Z]/ ? "[$_]" : $_ } split "", $word; say $new_word;'
[l][a][y][e][r]123 0.% [f][o][o]

[download]

In reply to Re: regex find and replace with a twist by dsheroh
in thread regex find and replace with a twist by Anonymous Monk

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