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Text::Xslate::Manual::FAQ - Frequently asked questions and answers



How do you pronounce Xslate?

We read it /eks-leit/.

What Xslate stands for?

It stands for XS template, a template engine written in XS, although pure Perl implementations are also provided.

What are 'Kolon', 'Metakolon', and 'TTerse' ?

Xslate supports several template syntaxes. Kolon is the default syntax, Metakolon is suitable to output Kolon templates, and TTerse is compatible with Template-Toolkit. You can specify the template syntax by passing syntax option to the Text::Xslate constructor.

    my $tx = Text::Xslate->new(
        syntax => 'TTerse', # by moniker

    my $tx = Text::Xslate->new(
        syntax => 'Text::Xslate::Syntax::TTerse', # by fully qualified name


How can I changes template tags?

Use start_tag, end_tag, and line_start options, which can be joined together with syntax option:

    my $tx = Text::Xslate->new(
        syntax     => 'TTerse',
        tag_start  => '{',
        tag_end    => '}',
        line_start => undef,
    print $tx->render_string('Hello, {lang} world!', { lang => 'Xslate' });

How can I iterate over HASH references?

Convert HASH references into ARRAY references because for methods can deal with ARRAY references.

    : # in Kolon
    : # iterate $hash by keys
    : for $hash.keys() -> $key {
        <: $key :>
    : }
    : # by values
    : for $hash.values() -> $value {
        <: $value :>
    : }
    : # by key-value pairs
    : for $hash.kv() -> $pair {
        <: $pair.key :>=<: $pair.value :>
    : }

Note that the above methods return ARRAY references sorted by the keys.

How can I use Template-Toolkit virtual methods and filters?

Xslate itself does not support these methods and filters, but there are modules on CPAN that implement them.

Text::Xslate::Bridge::TT2 provides almost all the TT methods and filters, but it requires Template-Toolkit itself.

Text::Xslate::Bridge::TT2Like provides the same features as Bridge::TT2, but it does not require the Template-Toolkit distribution.

These bridge modules are useful not only for TTerse users, but also for Kolon users.

How to limit while-loop like Template-Toolkit?

While Template-Toolkit has a loop counter to prevent runaway WHILE loop, Xslate has no arbitrary limitation.

Instead, you can use alarm() to limit any runaway code:

    eval {
        local $SIG{ALRM} = sub { die @_ };
        alarm(1); # set timeout
        $tx->render('<: while true { } :>', \%vars);
    if($@ =~ /\b ALRM \b/xms) {
        # timeout!

Functions, filters and macros

How can I use macros as a callback to high-level functions?

Macros are objects that overload &{}, the CODE dereference operator, so all you have to do is to call them, but don't check their types because they are not a real CODE reference.

    my $tx = Text::Xslate->new(
        function => {
            'count' => sub {
                my($a, $cb) = @_;
                # Don't check the type of $cb!
                return scalar grep { $cb->($_) } @{$a};

    print $tx->render_string('<: count($a, -> $x { $x >= 50 }) :>',
        { a => [ 0 .. 100 ] },
    ); # => 50