Have you tried it like this? 
my $patterns = "/path/to/file.txt";
my $arg1 = shift;

open( PATTERNS, "<", $patterns ) or die "$patterns: $!\n";
my @list_patterns = <PATTERNS>;
close PATTERNS;
chomp @list_patterns;

my $list_regex = join '|', @list_patterns;

open( FILE, "<", $arg1 ) or die "$arg1: $!\n";
while (<FILE>) {
    if ( /($list_regex)/ ) {
        print "\n$arg1\n$1\n";
    }
}

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If your list of patterns does not include anything that tries to match across a line-break (i.e.: "...\n..."), then you don't need to slurp your whole "arg1" file content into memory at one time. Depending on the files that you are searching through, that can save time by avoiding memory swaps, and depending on what sort of patterns you are looking for, applying the regex to a small string (one line at a time) could be a lot faster than applying it to a whole file.

If your patterns do involve matching across line breaks, loading them all into a single regex (joining them together with "|") will probably speed things up anyway, because you only do one regex match against the whole string.

In reply to Re: Comparing pattern by graff
in thread Comparing pattern by mrc

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