This isn't at all related to your actual problem, but what's the /g for? The * is already getting all of your matches.

And you probably have this already if you're benchmarking, but I suspect /g probably is the right way to go:

use warnings;
use strict;

gf ();
gf ();

sub gf
{
    my $ins1 = '4 A -4 C -4 B 1 D';
    my @inserts;
    $ins1 =~ /^[\d+-]+/g;
    push @inserts, $ins1 =~ /\G(?: \w ([\d+-]+))/g;
    print join(' ', @inserts), "\n";
}
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