Ah I was hoping someone would suggest eval(). I've been working on:

my $line = 0;
while (<>) {
    s/^([\smy]*\$\w+\s+\.?=\s+)['"](.*?)\\?n?['"];/$1<<END;\n$2/
        unless $line > 0;
    s/^\s*\$\w+\s+\.=\s+['"](.*?)\\?n?['"];$/$1/g;
    s/\\"/"/g;
    $line++;
    print $_;
}
print "END\n";
[download]

which works but is (I believe) a poor design. I'll play with your suggestion next. See my response to graff for why I can't jump right to template tags.