I've run into the same kind of thing, but it seems size-related in my case. I'm munging through several overly large (1-2GB) PST and MDB files, trying to do plaintext searches. When I do some pre-emptive cleanup, I get the error; I'm sure there's a better way to do this, but...

local $/ ;
open FILE, $file ;
my $data = <FILE> ; #yes, I have enough memory
close FILE ;

$data =~ s/[^[:ascii:]]+//g ;

while ($data =~ /($regex)/g)
{
...
}
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Any MS Office files under the 1GB mark seem to happily go through the cleanup - others die miserably with the [seemingly] unrecoverable "Substitution loop in..." error.

v5.8.8 built for x86_64-linux-thread-multi
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