Adding a key to SSH-Agent from within perl - perl

Question

OK, so here's what I'm trying to do. I'm writing a program that will retrieve a keepass database from my phone (via ssh) and search through it for whatever password I'm interested in. I'd like to use the same password for the keepass database as the ssh-key that I've made for retrieving the keepass database, but I don't want to enter the password twice. So. Here's what I thought: I'll write a perl script that asks for the password once (via ssh-askpass) (That's my readpass function at the bottom. It works fine.) I can read the keepass, via that key, etc, and all is good.
But, I can't seem to figure out how to add the ssh-add without it prompting me for the password for the key again when I try to ssh to the phone.
I tried making a shell script that would simply echo an environment variable, and then setting SSH_ASKPASS to that script, (and setting the password in an environment variable and system'ing that... Like this:
my $key = readpass();
$ENV{"SSH_ASKPASS_ENV"} = $key;
$ENV{"SSH_ASKPASS"} = "/home/user/bin/ssh-askpass-env";
system("/usr/bin/ssh-add /home/user/.ssh/keepass-retriever");
ssh-askpass-env simply has:
#! /bin/sh
echo "${SSH_ASKPASS_ENV}"
But, that doesn't seem to do it, it still asks me for my password. I can verify that ssh-askpass-env is being called, and that it is getting the password.
I guess my question is: How can I add a key to ssh-agent from within perl using a prespecified password? (Since I've just read the password from readpass() below)
Thanks!
sub readpass() {
my $passwd = undef;
if (defined($ENV{"DISPLAY"})) {
if (open(PASSWD, "/usr/bin/ssh-askpass 'KeePass' |")) {
chomp($passwd = <PASSWD>);
close(PASSWD);
}
}
else {
ReadMode('noecho');
printf("Enter keepass password: ");
$passwd = ReadLine(0);
chomp($passwd);
ReadMode('normal');
}
return($passwd);
}

Answer 1

After reading the ssh-add man page, I found detaching the terminal worked:
system("/usr/bin/ssh-add /home/user/.ssh/keepass-retriever < /dev/null &>/dev/null");