Passing an empty string in $_ creates an empty regexp pattern, as in "m//". This is a special case discussed in perlop, here:

The empty pattern //

If the PATTERN evaluates to the empty string, the last successfully matched regular expression is used instead.....If no match has previously succeeded, this will (silently) act instead as a genuine empty pattern (which will always match).

Your first match occurs in that vacuum of acting like a genuinely empty pattern, which will always match. The final test is like asking if "" =~ m/foo/, which doesn't match.


Dave

In reply to Re: grep trouble by davido
in thread grep trouble by LogMiner

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