Your code can be shrunk to:

for my $file (@ARGV ? @ARGV : '-') {
    my $fh;
    if ($file eq '-') {
       open($fh, '-');  # "-" doesn't work with 3-arg open.
       binmode($fh, ':utf8');
    } else {
       open($fh, '<:utf8', $file);
    }
    while (<$fh>) { do_whatever( $_ ) }
}
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Differences from using while (<>):

• eof() doesn't work the same.
• eof(ARGV) doesn't work.
• eof might not work the same.
• $. doesn't work the same.