Advanced multi-conditonal split with an regex in Perl

Question

I would like to split a string on multiple conditions such as:

• After each /;/
• After each /{/ or /}/
• After each /\w+:/ but not after /\w+:\s+\{/
• After each /#\w.*$/

I've found that I can keep a pattern and split before it with

/(?=pattern)/

or split after it (if the pattern has a fixed width)

/(?<=pattern)/

or split after it (if the pattern has a variable width)

/pattern\K/

or even remove the pattern during the operation

/pattern/

With all this knowledge I wrote this:

#!/usr/bin/perl    
$_ = do { local $/; <DATA> };
s/\#\w.+\n\K|\n//g;

my @content = split /(?:(?<=[;{}])|(?<=:)(?!\s*\{)|#\w.*\$\K)/, $_;

print join "\n", @content;

__DATA__
carrot;
#orange
apple: {pear; { cabbage; } }
#passion
sprout: celeri;
tomato;

Where the output should be this (after manually reindenting it):

carrot;
#orange
apple: {
  pear;
  {
    cabbage;
  }
}
#passion
sprout:
celeri;
tomato;

I am not really happy with this method for multiple reasons:

• I cannot use a x regex in split like split m/re/x to make the regex more readable
• I need to treat the exception for the special case /^\s*#.*$/ where I cannot remove CR otherwise I will get for instance #passionsprout:

Can I do a better job?

Answer 1

Think the other way around: try to add a newline to all characters that need one. That way your regex is a bit simpler.

#!/usr/bin/perl -w

use strict;

my $content = do { local $/; <DATA> };

my $regex = qr{
  (?m)
    (^
     |
     :\s*
    )
    \{                  # open curly brace preceded by 
                        # beginning of line
                        # OR
                        # colon

  |                     # OR
    [:;\}]              # any of these characters
    (?!\s*\n)           # NOT followed by newline
}x;

$content =~ s/($regex)/$1\n/g;
print $content, "\n";