Re: Best Practice for replace sub

[tobyink]

in reply to Best Practice for replace sub

Perl 5.10 and above have state variables, but they don't work for hashes and arrays - just scalars. Still, you can use hashrefs/arrayrefs.

sub encode {
    state $lookup = {
        '"' => '"',
        '&' => '&',
        '<' => '&lt;',
        '>' => '&gt;',
        map((chr($_), "&#$_;"), (0..31)),
    };
    state $re = do { my $tmp = join('', keys %$lookup); qr/([$tmp])/ }
+;
    
    my ($text) = @_;
    return '' unless defined $text;
    $text =~ s/$re/$lookup->{$1}/g;
    return $text;
}

If you need to support older versions of Perl, then curly braces can be used to limit the scope of lexical variables...

{
    my $lookup = {
        '"' => '"',
        '&' => '&',
        '<' => '&lt;',
        '>' => '&gt;',
        map((chr($_), "&#$_;"), (0..31)),
    };
    my $re = do { my $tmp = join('', keys %$lookup); qr/([$tmp])/ };
    
    sub encode {
        my ($text) = @_;
        return '' unless defined $text;
        $text =~ s/$re/$lookup->{$1}/g;
        return $text;
    }
}

Or even better (because it delays populating the variables until they're needed):

{
    my ($lookup, $re);

    sub encode {
        $lookup ||= {
            '"' => '"',
            '&' => '&',
            '<' => '&lt;',
            '>' => '&gt;',
            map((chr($_), "&#$_;"), (0..31)),
        };
        $re ||= do { my $tmp = join('', keys %$lookup); qr/([$tmp])/ }
+;
    
        my ($text) = @_;
        return '' unless defined $text;
        $text =~ s/$re/$lookup->{$1}/g;
        return $text;
    }
}