You're missing a call to binmode(),

The OP used :raw in the open, a suitable alternative.

#!perl -l

open(my $fh, '<', $0);
print(substr(<$fh>, -2) eq "\r\n" ?'bin':'txt');  # txt

open(my $fh, '<', $0);
binmode($fh);
print(substr(<$fh>, -2) eq "\r\n" ?'bin':'txt');  # bin

open(my $fh, '<', $0);
binmode($fh, ':raw');
print(substr(<$fh>, -2) eq "\r\n" ?'bin':'txt');  # bin

open(my $fh, '<:raw', $0);
print(substr(<$fh>, -2) eq "\r\n" ?'bin':'txt');  # bin
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