Changing an array in Perl

Question

I am trying to use Perl to parse output from a (C-based) program. Every output line is a (1D) Perl array, which I sometimes want to store (based on certain conditions).

I now wish to (deep) copy an array when its first element has a certain keyword, and print that same copied array if another keyword matches in a later line-array.

So far, I have attempted the following:

#!/usr/bin/env perl
use strict; # recommended
use Storable qw(dclone);
...
while(1)   # loop over the lines
    {
        # subsequent calls to tbse_line contain
        # (references to) arrays of data 
        my $la = $population->tbse_line();
        my @copy;
        my $header = shift @$la;

        # break out of the loop:
        last if ($header eq 'fin');

        if($header eq 'keyword')
        {
            @copy = @{ dclone \@$la };
        }

        if($header eq 'other_keyword')
        {
            print "second condition met, print first line:\n"
            print "@copy\n";
        }
    }

However, this prints an empty line to the screen, instead of the contents of the copied array. I don't have a lot of Perl experience, and I can't figure out what I am doing wrong.

Any idea on how to go about this?

We don't know what ->tbse_line() returns.

choroba
– choroba

2018-11-19 17:46:28 +00:00
Commented Nov 19, 2018 at 17:46 — choroba
– choroba, Commented Nov 19, 2018 at 17:46

mob · Accepted Answer · 2018-11-19 17:48:21Z

5

my @copy allocates a new Perl array named @copy in the current scope. It looks like you want to set @copy during one iteration of your while loop and print it in a different iteration. In order for your array not to be erased each time a new while loop iteration starts, you should move the my @copy declaration outside of the loop.

my @copy;
while (1) { ... }

answered Nov 19, 2018 at 17:48

mob

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2 Comments

Final_Sun Over a year ago

Thanks, that fixed the issue! The code above is just a small part of a very large code that I did not write myself, but am trying to adapt to my current processing needs. I must have overlooked the positioning of the array declaration.

Grinnz Over a year ago

You should accept the answer if it's solved your problem :)

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