File handles and loops

[dr.jekyllandme]

Hello, I am trying to write a program that will allow a user to edit a file using editor. Once the user quits the editor, I am going to parse the file to make sure that the expected format of this file has been followed. If not, my program will print out an error message for the line number and reopen the file to allow the user to correct their mistakes. This will go on until they have correctly conformed to the expected format. For example, my rule is that all lines should begin with a lowercase letter. My code so far does this, but I know that I am messing up on dealing with file handles. I am using a loop to parse each line of my file to make sure the string is valid. If it is not, I close my current file handle and allow another edit to occur. Below is my code so far:

my $string = join( "\n", qw(howdy partner goodbye Friend saynora adios
+ Amigo) );
open(MY_FILE, '>my_file.txt');
print MY_FILE $string;
close(MY_FILE);
&edit_file('my_file.txt');

sub edit_file {
    my $my_file = shift;
    my $editor = $ENV{'editor'};
    system('vim', $my_file);
    my $validate = &validate_file($my_file);
    print "File is ok\n" if $validate;
}

sub validate_file {
    my $my_file = shift;
    open( MY_FILE, $my_file ) or die "Unable to open file\n";
    while( <MY_FILE> ) { 
        chomp( $_ );
        unless( $_ =~ /^[a-z]/ ) { 
            close( MY_FILE );
            print "Error at line $.\n";
            print "$_ does not begin with a lower case letter\n";
            print "Hit return to continue: ";
            <STDIN>;
            &edit_file( $my_file );
        }   
    }   
    close( MY_FILE );
    return 1;
}

I am not sure if my approach is correct. If anyone can give me pointers how to improve my code, it would be great. Thank you.