my @variables = $_ =~ m/<\?--(\S+?)-->/g;

##</code><code>##

my @variables = $line =~ /<\?--(\S+?)-->/g;

##</code><code>##

my @variables = /<\?--(\S+?)-->/g;

##</code><code>##

  for my $variable ( @variables ){
    # replace the tag with the value of the variable
    # if there is one.
    s/<\?--$variable-->/$$variable/g if $$variable;
  }