Just as samtregar suggested, a two-pass approach seemed right to me too. First pass, parse(), parses the data into a hashref, and the second pass, get_command_args(), extracts the data from the hash ref to build the list of command arguments.

Two recursive subroutines in one perl program. I think I've been doing too much emacs lisp :-)

use strict;
use warnings FATAL => 'all';

chomp (my @config = <DATA>);

my $config = parse();
for my $server ( keys %$config ) {
    my @args = get_command_args( $config->{$server} );
    print "enable $server $_\n"
      for @args;
}

sub get_command_args {
    my $cfg = shift;

    my @arg_list;
    for my $k ( keys %$cfg ) {
        my $v = $cfg->{$k};

        my $args = "$k ";
        if ( ref $v ) {
            $args .= join " ", get_command_args( $v );
        }
        else {
            $args .= "$v ";
        }
        push @arg_list, $args;
    }
    return @arg_list;
}

sub parse {
    my $hash;
    while ( my $line = shift @config ) {
        if ( $line =~ /(\S.*\S) \s* \{/x ) {                # keywords
+ {
            my $k = $1;
            $hash->{$k} = parse();
        }
        elsif ( $line =~ /(\S+) \s+ (\S+) \s* ; \s* $/x ) { # key valu
+e;
            $hash->{$1} = $2;
        }
        elsif ( $line =~ /^ \s* } \s* $/x ) {               # }
            return $hash;
        }
        else { die $line }                                  # can't ha
+ppen!
    }
    return $hash;
}

__DATA__
server {
    hostname test;
    console-type {
        type vt100;
    }
    account root {
        authentication-type {
             password "bubba";
        }
    }
}
[download]

Output:

enable server account root authentication-type password "bubba"
enable server hostname test
enable server console-type type vt100
[download]