Perl Regular Expression to match special characters - regex

Question

I have the below code in which I am checking for a specific variable location in an array excluded.It works fine with all the array elements except one (abc/def/libraries/linux_3.2.60-1+deb7u3.dsc). When I provide this element as my location its printing "location not excluded" , even though its excluded.
How can I made my code to get this element as well as excluded?
use strict;
use warnings;
my #excluded = (
"xyz/efg/headers/",
"abc/def/libraries/jni-mr.h",
"abc/def/libraries/linux_3.2.60-1+deb7u3.dsc",
);
my $location = "abc/def/libraries/linux_3.2.60-1+deb7u3.dsc";
my $badpath = 0;
foreach (#excluded) {
# -- Check if location is contained in excluded array
if ($location =~ /^$_/) {
$badpath = 1;
print "location is excluded : $location \n";
}
}
if (! $badpath) {
print "location is not excluded : $location \n";
}
Desired Output:
location is excluded : abc/def/libraries/linux_3.2.60-1+deb7u3.dsc
Current Output:
location is not excluded : abc/def/libraries/linux_3.2.60-1+deb7u3.dsc

Answer 1

Use quotemeta($text) or \Q$text\E (inside double quotes or a regex literal) to create a pattern that matches the value of $text. In other words, use
if ($location =~ /^\Q$_\E/)
instead of:
if ($location =~ /^$_/)

Answer 2

It looks like you intend to define your exclusions by regex, but you have not escaped regex metachars properly in those regexes. For your failing case, the metachar causing it to fail is the plus (+), which is a one-or-more multiplier in most regex flavors (including Perl), but you need to match it literally.
Also, I'd recommend moving the ^ anchor from the loop to each individual regex, which would make the code more flexible, in that you could choose not to anchor some of the exclusion regexes if you wanted.
Also, you should use the qr() construct, which allows you to precompile regexes, saving on CPU.
Also, this requirement is a good candidate for using grep().
use strict;
use warnings;
my #excluded = (
qr(^xyz/efg/headers/),
qr(^abc/def/libraries/jni-mr\.h),
qr(^abc/def/libraries/linux_3\.2\.60-1\+deb7u3\.dsc),
);
my $location = 'abc/def/libraries/linux_3.2.60-1+deb7u3.dsc';
# -- Check if location is contained in excluded array
my $badpath = scalar(grep($location =~ $_, #excluded )) >= 1 ? 1 : 0;
if ($badpath) {
print "location is excluded : $location \n";
} else {
print "location is not excluded : $location \n";
}