Dang. I was hoping it was something wrong with my code, and therefore fixable. Unfortunately, for the intent & purpose of my particular script I'm stuck with 5.10. Network distribution and company policy and all that.

I will try it out on a newer version when I get the chance and report back, though.

In the meantime, I've found a quick n'dirty fix in case anyone else encounters this archaic headache. Just switch to @+ and @- instead of the more convenient %+:

#!/usr/bin/perl
use strict;
use warnings;

open(my $fh, '<', 'EXAMPLE.TXT');

my $regexp = qr/(?<value1>\d+)\s+(?<value2>\d+)/;

while(<$fh>)
{
    next unless /$regexp/;
    my $value1 = substr($_, $-[1], $+[1] - $-[1]);
    my $value2 = substr($_, $-[2], $+[2] - $-[2]);
    print "GOT $value1 $value2\n";
}
[download]

And thanks for the responses!