gfx.pl

#!perl -w
use strict;
use Text::Xslate;
use Text::Xslate::Util qw(hash_with_default);
my $DEBUG = 1;

# bad pratice
{
    my %vars;
    my $vars_ref = $DEBUG ? hash_with_default(
        \%vars,
        sub { "FILL ME/$_[0]" }
    ) : \%vars;

    my $tx = Text::Xslate->new();
    print $tx->render_string(<<'T', $vars_ref);
Hello, <: if ($oops) { :>sursen<: } :> world!
T
    # => Hello, sursen world!
}

# best practice
{
    my %vars;
    my $vars_ref = $DEBUG ? hash_with_default(
        \%vars,
        sub {
            Text::Xslate->print(
                Text::Xslate::mark_raw('<span style="color: red; font-size: 1.8em;">'),
                "FILL ME/$_[0]",
                Text::Xslate::mark_raw('</span>')
            );
            return undef;
        }
    ) : \%vars;

    my $tx = Text::Xslate->new();
    print $tx->render_string(<<'T', $vars_ref);
Hello, <: if ($oops) { :>sursen<: } :> world!
T
    # => Hello, <span style="color: red; font-size: 1.8em;">FILL ME/oops</span> world!
}

# great                                                                                                                                                                       
sub hash_with_default_walker {
    my($base_key, %hash) = @_;
    my $result = {};
    for my $key (keys %hash) {
        if (ref($hash{$key}) eq 'HASH') {
            $result->{$key} = hash_with_default_walker("$base_key$key.", %{ $hash{$key} });
        } else {
            $result->{$key} = $hash{$key};
        }
    }
    hash_with_default(
        $result,
        sub {
            Text::Xslate->print(
                Text::Xslate::mark_raw('<span style="color: red; font-size: 1.8em;">'),
                "FILL ME/$base_key$_[0]",
                Text::Xslate::mark_raw('</span>')
            );
            return undef;
        }
    );
}

{
    my $vars_ref = hash_with_default_walker('', hash => +{ foo => +{ a => 1 } });
    my $tx = Text::Xslate->new();
    print $tx->render_string(<<'T', $vars_ref);
Hello, <: if ($oops) { :>sursen<: } :> world!                                                                                                                                 
Hello, <: if ($hash.foo.a) { :>sursen<: } :> world!                                                                                                                           
Hello, <: if ($hash.foo.b) { :>sursen<: } :> world!                                                                                                                           
T                                                                                                                                                                             
    # => Hello, <span style="color: red; font-size: 1.8em;">FILL ME/oops</span> world!                                                                                        
    # => Hello, sursen world!                                                                                                                                                 
    # => Hello, <span style="color: red; font-size: 1.8em;">FILL ME/hash.foo.b</span> world!                                                                                  
}