I want to use a one-liner to print a middle section of a file by using a state variable to indicate whether the current line is within the desired section of the file. But I am unable to initialize the state variable. Initialization is so simple, and I just cannot find what the problem is. Please help. Thanks.
The file is name testFile.txt and has the following lines:
section 0; state 0; not needed
= start section 1 =
state 1; needed
= end section 1 =
section 2; state 2; not needed
And my one-liner is
cat testFile.txt | perl6 -ne ' state $x = 0; say "$x--> "; if $_ ~~ m/ "start" / { $x=1; }; if $x == 1 { .say; }; if $_ ~~ m/ "end" / { $x = 2; }'
And the output showed that $x=0 is not doing initialization:
Use of uninitialized value $x of type Any in string context.
Methods .^name, .perl, .gist, or .say can be used to stringify it to something meaningful.
in block at -e line 1
-->
Use of uninitialized value of type Any in numeric context
in block at -e line 1
Use of uninitialized value $x of type Any in string context.
Methods .^name, .perl, .gist, or .say can be used to stringify it to something meaningful.
in block at -e line 1
-->
= start section 1 =
1-->
state 1; needed
1-->
= end section 1 =
2-->
2-->
This looks like a bug to me: Apparently,
-n
does not properly set up a lexical environment.As a workaround, you can wrap the whole things in a block, eg by surrounding your code with
do { ... }
or even just{ ... }
.Also note that depending on your use case, the whole thing can probably be simplified by using the flip-flop operator, eg