sub bracket {
   local $_ = @_ ? $_[0] : $_;
   return "[ $_ ]";
}

sub quote {
   local $_ = @_ ? $_[0] : $_;
   s/(["\\])/\\$1/g;
   return qq{"$_"};
}

@{$_[0]->{'images'}{'section_a'}} = (
   [ "image1.gif" , "mark('a',1)" ],
   [ "image2.gif" , "mark('a',2)" ],
);

print(
   bracket            # Put brackets around the row.
   join ',',          # Join the records.
   map {              # For each record,
      bracket         #    Put brackets around each record.
      join ',',       #    Join the fields.
      map quote, @$_  #    Quote and escape the fields.
   } @{$_[0]->{'images'}{'section_a'}}
);

__END__
output
======
[ [ "image1.gif","mark('a',1)" ],[ "image2.gif","mark('a',2)" ] ]