ok I added the whole code

PS. Modifying your code, here is a simple version that reproduces the error: 

sub butter {
    my $_ = shift;
    return $1 + butter($_) if s/(\d+)//;
    return 0;
}

print butter 'effect / 7ACV06';

[download]

In reply to Re^2: $1 not "freezing" in an addition by grondilu
in thread $1 not "freezing" in an addition by grondilu

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