qr operation in perl 5.16

Question

I am trying to fix a very old script, which is trying to find a string FILE_DESC_LIMIT in a text file and change it to something else.

For this my current s

Answer 1

See Regular Expressions in Perl 5.14 Delta: the (?^ now signifies default modifiers. It's just a matter of how the compiled regular expressions are serialized, the more important is the difference between \b and ^ in your regular expressions.