though i am not sure if this the right approach, but you can do something like the following or get some ideas, who knows:

use strict;
use warnings;
use diagnostics;
use File::Slurp;

my @files = read_dir($ARGV[0]); #read files in dir into an array
my $dir = $ARGV[0];

my $string = $ARGV[1];

my $file;
my $line;

foreach my $element (@files) {
    open $file, '<', "$dir/$element"; #open each file

        while (<$file>) {
            if ( $_ =~ $string ) { #match your string
                print "found $string in $element\n";
            }
        }
    close $file;
}
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this will read each file into an array, then it will open each of those files and search for a match.

EDIT: in your test script in your original post, you may want to look into Cwd. i think that would allow you to get the current working directory AFTER you leave the dir that the script is in. and would only be slightly trivial to implement without a major code change