tab@music3:~/2018-0717$ cat !$
cat pm2.pl
#!/usr/bin/perl

use strict;
use warnings;

{
  my $word = q($-.%abc&/);

  my @group1 = ( $word =~
    m/(?:            # Non-capturing group of captured
      ([^a-zA-Z]+)   # .. non-matching
      ([a-zA-Z]+)    # .. following by matching
     )+              # .. for as many groups as possible
     ([^a-zA-Z]+)    # followed by matching.
    /x );

    my @group2 =
      map { $_ =~ /[a-zA-Z]/ ? split( //, $_ ) : $_ } @group1;

    my $new_word = join ( '', map { "[$_]" } @group2 );

    print "$word -> $new_word\n";
}
tab@music3:~/2018-0717$ perl pm2.pl
$-.%abc&/ -> [$-.%][a][b][c][&/]
tab@music3:~/2018-0717$