The following makes a single pass over the input file (I have used in-file DATA for convenience. You will, of course, have to change this to read from your data file):

use strict;
use warnings;

my (%tags_to_match, @extracted_tags);
my  $in_matching =  0;
my  $tag_prefix  = 'bbc_';
my  $tag_regex   =  qr{ ( $tag_prefix \w+ _ \d+ ) }x;

while (my $line = <DATA>)
{
    if ($in_matching)
    {
        if ($line =~ / ^ \s* \[ end \] \s* $ /x)
        {
            $in_matching = 0;
        }
        elsif ($line =~ $tag_regex)
        {
            $tags_to_match{ $1 }++;
        }
    }
    elsif ($line =~ / ^ \s* \[ start \] \s* $ /x)
    {
        $in_matching = 1;
    }
    elsif ($line =~ $tag_regex)
    {
        my $tag = $1;

        foreach (keys %tags_to_match)
        {
            if ($tag eq $_)
            {
                push @extracted_tags, $tag;
                last;
            }
        }
    }
}

say "\@extracted_tags = ", join(', ', @extracted_tags);

__DATA__
[start]
bbc_arc_001
bbc_arc_002
abc_arc_001
[end]

bbc_arc_001
bbc_arc_002
bbc_arc_003
bbc_arc_004

[download]

This should work provided the tags to be extracted always appear after the start/end block in which they are specified. If this is not the case for your input file, you will need to make two passes over the file: the first to read the contents of the start/end block(s), the second to extract the specified tags.

Also note that your regex may not be doing what you wanted. [a-zA-Z]*[0-9]*_* means: zero or more letters, followed by zero or more digits, followed by zero or more underscores. In my code I use a regex which is a guess at what was intended.

HTH,

Athanasius <°(((>< contra mundum

In reply to Re: Extract Tags between Two strings by Athanasius
in thread Extract Tags between Two strings by stallion

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