I've use this in my code before:

#actual data came over the network with inconstant line ends.
my $text = "some\r\nmulti-line\ntext";
my $line_count = $text =~ s/\r?\n/\n/g;
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There were cenrtanly a dozen other ways to get the line count, but for what was being done this was the most strait forward, without doing double work.