my $file_from = 'test.txt';
my $file_to = 'test.gpg';

my $password = ' Blaaah';

open (my $FH, qq(| gpg --batch --passphrase-fd 0 -o "$file_to" --symmetric --cipher-algo AES256 "$file_from") );
print $FH $password;
close $FH or die $!;