Question

I am trying to write a regex to recognize a single line of text, with underscore ( _ ) recognized as a line continuation character. For example, “foo_\nbar” should be considered a single line, because the “foo” ends in an underscore. I am trying:

$txt = "foo_\nbar";
print "$&\n" if $txt =~ /.*(_\n.*)*/;

However, this prints only:

foo_

This seems to violate the “leftmost longest” rule for Perl regexes!

Interestingly, if I remove the last star (*) in the regex, i.e.:

$txt = "foo_\nbar";
print "$&\n" if $txt =~ /.*(_\n.*)/;

it does print:

foo_
bar

But I need the star to recognize “0 or more” continuations!

What am I doing wrong?

Answer 1

Why is this happening was explained by @ysth. To fix it you may use the following regex:

/([^_\n]|_.)*/s