use 5.20.0;
use warnings;

use Path::Tiny;

use experimental qw/
    signatures
    postderef
/;

my @lines = path(shift)->lines;

print scalar grep { is_valid($_) } @lines;

sub is_valid($line) {
    $line =~ /(?<min>\d+)-(?<max>\d+) (?<letter>\w): (?<password>\w+)/;

    return 1 == grep { $_ eq $+{letter} }
                    (split '', $+{password})[ map { $_ -1 } @+{'min','max'} ];
}