You probably don't run all the lines together in one script, but you include the first line and then just one of the second, third, or fourth one. It would have helped us to help you if you described in more detail what your code section meant.

The main problem is context. Both print on line 2 and list assignment on line 4 force list context, which means the whole contents of the file is returned from the readline. Line 3 uses readline in the binding operator which forces scalar context, which means it only reads one line from the file. If the very first line doesn't contain the error, it won't be printed.

Inserted: To shorten the code, you can use 

print grep /error/, <$f>;

[download]
as grep also forces list context to its non-first argument(s).

Some other comments:

  1. Don't use my $a. $a is a special variable used in sort, lexicalising it can lead to sort not working.
  2. Check the return value of open and use the 3 argument variant: 
    open my $f, '<', 'file' or die $!;

    [download]

map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

In reply to Re: Grepping the filehandler by choroba
in thread Grepping the filehandler by arunkumar.rk141

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