#!/usr/bin/perl

use strict;
use warnings;

my %in;
my %out;
my $testsub;
my $constant = "fixed";

$in{cid} = 12345;
$out{this}{that}[0] = 678;
$testsub = sub { return "this is foobar" };

print "normally, \$testsub returns: " . &$testsub . "\n\n";
while (<DATA>) {
    s/(?<=')(\$[^']+)/(ref($1) eq 'CODE') ? &{$1} : $1/ee;
    print;
}

__DATA__
select field from table where id!='$in{cid}'
update table set field = null where id = '$out{this}{that}[0]'
delete from table where value = '$constant'
select something from somewhere where status='$testsub'