The statement: 
   ! /def/

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compares "def" with $_ .

$_ is defined in your one-liner (By the existance of -n in the perl command)

But $_ is undefined in the "full script".

Perhaps you meant: 

(my $B = $A ) !~ /def/ and print $B;

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which compares the contents of $A/$B.

        The best defense against logic is ignorance.

In reply to Re: Regex match on implicit default variable ($_) in a script, not a one liner by NetWallah
in thread Regex match on implicit default variable ($_) in a script, not a one liner by Todd Chester

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