multiple backreferences in a substitution

wrinkles has asked for the wisdom of the Perl Monks concerning the following question:

Gentle Monks,

I wrote a (perl6) script that collects class definitions from the HTML head in a hash, and inlines the style by substitution into the body. Here's the substitution:

UPDATE: match is actually coming from the "if" and "while" statements, not the repeated regex as I thought. Works without capture braces in repeated block. Yikes, never mind!

repeat {  # Replace class with inline styles (repeatedly)
    $new ~~ s/  class \= \"  \w+  \" / style="%classes{ $0.Str }" /;
} while $new ~~ /  class \= \" (\w+) \" /;
[download]

Yes it works, I'm just not convinced there isn't a slicker way. In particular, is there a simple way to substitute a capture at the corresponding match location, using a global substitution ( or something else entirely)?

TIA! The full script is below:

#!/usr/bin/env perl6
use v6;

# Takes vim html export as input.
# Outputs html file with css class styles inlined.
# Regexp depend on precise whitespace output of Vim export.
# Also depends on html format where each span has a single class defin
+ition. 

sub MAIN($in, $out) {
    my %classes;
    my $out_fh = open $out, :w;
    for $in.IO.lines -> $line {
        # Between style tags of the html head 
        if ( $line ~~ /^ \< style / ) ^fff^ ( $line ~~ /^ \< \/ style 
+/ ) {
            # Capture class definitions
            $line ~~ /^ \. ( \w+ ) \s+ \{ \s+ ( .* ) \s+ \} /;
            if ( $0 and $1) {                # If found class definiti
+on
                %classes{ $0.Str } = ~ $1       #    - save to hash
            } else { $out_fh.say("$line") }; # Otherwise just pass lin
+e to file
        # Class is declared in body
        } elsif $line ~~ / class \= \" (\w+) \" / {
            my $new = $line;
            repeat {  # Replace class with inline styles (repeatedly)
                $new ~~ s/  class \= \" (\w+) \" / style="%classes{ $0
+.Str }" /;
            } while $new ~~ /  class \= \" (\w+) \" /;
           $out_fh.say("$new") if $new;      # And write changes to fi
+le
        # No class definitions or declarations
        } else {
            $out_fh.say("$line");   # pass line unaltered
        }
    }
    close $out_fh;
};
[download]

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Re: multiple backreferences in a substitution by FreeBeerReekingMonk (Deacon) on Jun 30, 2015 at 20:42 UTC
I do not understand the question, you mean that this (removing the repeat-while loop) does not work for you? `# repeat { # Replace class with inline styles (repeatedly) $new ~~ s/ class \= \" (\w+) \" / style="%classes{ $0.Str }" /; # } while $new ~~ / class \= \" (\w+) \" /;` [download] Or do you mean you want to make it work for multi class stuff like: `<span class="foo bar">lorem</span>`	[reply] [d/l] [select]