You'd be better off (and more efficient) to code that as

$LINE = '';
...
$LINE .= $_ if /^DATA\:/;
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Thanks for the tip

While we're on the subject of efficiency, how could I make this a little more efficient?

if ($_ =~ /^FOO \=/) {
        $_ =~ s/^FOO \=\s//;
        $_ =~ s/\\$//;
        push @array, $_;
    }
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Firstly, you don't need to reference $_ for the m// or the s///, as it is the default. Second, you can capture the bit you want in the m//. It's also better to use a different delimiter if you have /'s in your regex

push @array, $1 if m[^FOO\s=\s(.*?)/$];
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should capture everything after the first space after the '=' and before the trailing '/'. If the number of spaces might vary then

push @array, $1 if m[^FOO\s+=\s+(.*?)/$];
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This wouldn't harm if there is only one space before and after.

---

Examine what is said, not who speaks.

if (s/^FOO =\s//){
    s/\\$//;
    push @array, $_;
}
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Basically, the only real change for efficiency is to do the replace once instead of twice. The rest is style, though style counts. I might suggest, though, making the first one a bit less strict, something like

if (s/^FOO\s*=\s*//){
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So it doesn't matter if there's more than one space, or a tab, or...whatever. But that's for your code to do with as it will.

Is there a way to initialize the variable with a value before I join it

You are also using join to do concatenation of two strings. Much better to use the "." operator which expresses exactly what you are doing:

$LINE = $LINE . $_;
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or even more succinctly

$LINE .= $_;
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The big win with the second is not that it is shorter to write, it is that it executes more efficiently because you do not have to recopy the existing string. Try this:

my $t = '';
$t .= "test" for 1..50_000;
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versus

my $t = '';
$t = $t . "test" for 1..50_000;
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See what I mean?

use warnings;
use strict;
my ($str,$x,$y,$c,$d);
$str.=chr($_) for 65..90;
$x++;
--$y;
$c += 10;    
$d -= 2;
print "$str $x $y $c $d\n";
__END__
ABCDEFGHIJKLMNOPQRSTUVWXYZ 1 -1 10 -2
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$hash{foo}.=$foo;
next if $dupe{$_}++;
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And just to nitpick, but there's no recursion in your example. ;-)

--- demerphq
my friends call me, usually because I'm late....