Regex placeholders

Recently, I worked on parsing data using Perl regexes. The task involved extracting specific information from matches. Here’s an example scenario:

id: 1   label: Button
id: 2   label: Radiobutton
id: 3   label: Checkbox

The goal was to create a mapping between label and id. Solution can look like this:

my %label_to_id = ();
while($items =~ /id: \s* (?<id>\d+) \s+ label: \s* (?<label>.*?)$/gmx) {
    $label_to_id{ $+{label} } = $+{id};
}

The regex is pretty straightforward, but few bits are worth explanation.

1. Regex Details:
   • The x modifier enhances readability by allowing whitespace and comments in the regex.
   • Explicit whitespace (\s*) is required where necessary.
   • Named captures ((?<name> ...)) store matched values in the %+ hash for easy access.
2. Match Iteration:
   • The g modifier finds all matches, enabling iteration with while to process each match.
3. Named Captures vs Positional:
   • Named captures ($+{name}) are clearer than positional captures ($1, $2), especially in complex patterns.

When dumping %label_to_id, we get the expected output:

{ Button => 1, Checkbox => 3, Radiobutton => 2 }