I've accidentally deleted a PlantUML file but luckily SVG output had them embedded

restore-source-from-plantuml-svg.pl

#!/usr/bin/perl
use v5.36;
use autodie;
use HTML::TokeParser ();
use MIME::Base64 qw(encode_base64 decode_base64);
use Compress::Zlib qw(deflateInit inflateInit);

main() if  $0 eq __FILE__;

sub main() {
    for (glob '*.svg') {
        print "$_: ";
        if (extract($_)) {
            say "ok";
        } else {
            say "skipped";
        }
    }
}

sub extract($filename) {
    my $encoded = find_src($filename) or return 0;
    my $src = decode_part($encoded) or return 0;

    open my $fh, ">", "$filename.txt";
    $fh->print("\@startuml \"$filename\"\n", $src, "\n\@enduml");
    1;
}

sub decode_part($part) {
    my $tr = $part =~ tr{-_0-9A-Za-z}{+/A-Za-z0-9}r;
    my $bin = "\x78\x9c" . decode_base64($tr);
    scalar inflateInit()->inflate($bin);
}

sub find_src_comment($filename) {
    open my $fh, "<:utf8", $filename;
    my $parser = HTML::TokeParser->new($fh);
    while (my $token = $parser->get_token) {
        if ($token->[0] eq 'C' && $token->[1] =~ /<!--SRC=\[([^\]]+)/) {
            return $1;
        }
    }
    warn "couldn't find the PlantUML source embedded in $filename"
}

After I've written this script, I've found out that PlantUML has the functionality: java -jar plantuml.jar -metadata foo.svg > foo.puml.txt.