Global matching and parser progress

The idea

The global match modifier supports repeated extraction. In list context, a global match can collect captures; in scalar context, successive successful matches advance the string’s match position. This state belongs to the target string and matters when loops or helper routines reuse it. A failed ordinary global match resets the position unless the keep-position behavior is requested.

Extracting every valid token does not prove that the whole input is valid: unmatched gaps can still be ignored. A strict parser should require progress from the previous position and verify that all input was consumed. Choose patterns that cannot repeatedly succeed without useful progress, and copy captured values immediately when later matches could overwrite the capture variables.

use strict; use warnings;
my $text="a12 b7";
my @numbers=($text =~ /([0-9]+)/g);
print join(",",@numbers),"\n";

12,7

List-context global matching collects the numeric captures, but this alone does not validate the spaces or letter prefixes.