You've been given excellent tips for improving your script. In an earlier response to you, Laurent_R suggested two methods for accomplishing your task. The following addresses one of those, as I think it's a good option.

When you're looking for keywords in each line, you're effectively joining them with OR. For example: print the current file's line if it contains 'Hello' OR 'world' OR 'today'. In a regex, the OR function is accomplished using alternation:

/(?:Hello|world|today)/
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The (?:) notation forms a non-capturing group. It's not strictly necessary here, but is used to just cluster the set of disjuncts.

There are a few issues with the above regex which need to be addressed. One is that, as it is, it's case sensitive. That is, 'today' would match but 'Today' wouldn't. To create a case-insensitive match, use the i modifier:

/(?:Hello|world|today)/i
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The next issue is that the above regex would match 'worldly'--and you may not want in-string matching. To prevent in-string matching, you need to match words enclosed by word boundaries:

/(?:\bHello\b|\bworld\b|\btoday\b)/i
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The last item to consider comes when you may want to match a phrase like 'Mr. Smith'. The problem is that the period in the string is a regex meta-character used to match one character. This period, and other meta-characters, must be escaped for a literal match: 'Mr\. Smith'.

Give the above considerations, the script below implements them:

use strict;
use warnings;
use autodie;

my @arr;
my $logz = '/var/log/syslog';
my $file = '/home/user/Desktop/keywords';

open my $keysFH, '<', $file;
while (<$keysFH>) {
    chomp;
    push @arr, "\\b\Q$_\E\\b";
}
close $keysFH;

my $words = '(?:' . ( join '|', @arr ) . ')';
my $regex = qr/$words/i;

open my $logFH, '<', $logz;
while (<$logFH>) {
    print if /$regex/;
}
close $logFH;
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The "\\b\Q$_\E\\b" notation first quotes all meta-characters in the word (\Q...\E) and the \\b means word boundary. There are two "\", because the first escapes the second, leaving the literal "\b" in the string.

Print both $words and $regex to see what's constructed.

Usage: perl script.pl [>outFile]

The last, optional parameter directs output to a file.

Hope this helps!

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