1.Search a file for a common user entered phrase. 2.Loop through each file within a directory for a user entered phrase.

use strict;
use warnings;
use File::Slurp qw(read_dir);
my $phrase = shift;
for my $file (grep { -f } read_dir('./')) {
    open my $fh, '<', $file or die "can not open $file: $!";
    while (<$fh>) {
        print if /$phrase/;
    }
    close $fh;
}
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See also perlintro (especially Files and I/O), File::Slurp and grep.

The Monastery has its own Tutorials to complement those on the official documentation website: Getting Started with Perl

1. grep PHRASE file
2. grep PHRASE *
3. grep -r PHRASE rootdir