use strict;
use warnings;

my $string = 'word_one word_one word_two 2000 word_three 3000';

while ( $string =~ m/(?<Word>\w+)\s+(?<Digit>\w+)/g ) {
	my %groupNames;
	push @{ $groupNames{ $+{$_} } }, $_ for keys %+;
	print "Match : $1 GroupName(s): @{ $groupNames{$1} }\n";
}

##</code><code>##

Match : word_one GroupName(s): Word Digit
Match : word_two GroupName(s): Word
Match : word_three GroupName(s): Word