The problem lies in the word "file", where "fi" can be represented by a ligature. Adding single /a doesn't help, but /aa solves the problem. So, if you don't work with unicode, you can just run your scripts like 
perl -Mre=/aa -e 'my $var = "hello"; $var =~ s!(?<=\D[01] file)s!!ig;'

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In reply to Re: Lookbehind issues with unicode by choroba
in thread Lookbehind issues with unicode by mrbark

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