/tmp>cat password-keeper.c
#include <stdio.h>

int main(int argc, char ** argv)
{
        // note: security checks omitted
        // note: deobfuscation omitted
        fputs("postgres",stdout);
        return 0;
}

/tmp>make password-keeper
cc     password-keeper.c   -o password-keeper

/tmp>strip password-keeper

/tmp>cat victim.pl
#!/usr/bin/perl

use strict;
use warnings;
use DBI;

my $dbh=DBI->connect('dbi:Pg:dbname=postgres','postgres',`./password-keeper`,{ RaiseError => 1 });
my $sth=$dbh->prepare('select 42 as answer');
$sth->execute();
$sth->dump_results();

/tmp>strace -f -o trace.txt -e trace=write,process perl victim.pl
42
1 rows

/tmp>cat trace.txt
26962 execve("/usr/local/bin/perl", ["perl", "victim.pl"], [/* 40 vars */]) = 0
26962 arch_prctl(ARCH_SET_FS, 0x7f04ca5ce700) = 0
26962 clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f04ca5ce9d0) = 26963
26963 execve("./password-keeper", ["./password-keeper"], [/* 40 vars */]) = 0
26963 arch_prctl(ARCH_SET_FS, 0x7f7d4ad21700) = 0
26963 write(1, "postgres", 8)           = 8
26963 exit_group(0)                     = ?
26963 +++ exited with 0 +++
26962 --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=26963, si_uid=1001, si_status=0, si_utime=0, si_stime=0} ---
26962 wait4(26963, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 26963
26962 write(1, "42\n1 rows\n", 10)      = 10
26962 exit_group(0)                     = ?
26962 +++ exited with 0 +++

/tmp>