I think some nasties could be concocted with unlink or rename.

I's not sure what you're doing with the nested quotations, s/$this/qq{qq{$with}}/gee. It seems like $with is all that's needed there to do what you want.

This strikes me as a dangerous thing, not easily untainted.

Added: Ah, now I see, the nested quotes isolate the replacement expression from actual execution. Nice!.

$ perl -e'$with=q(print "baz");$_="foobar";s/(foo)(bar)/qq(qq($with))/
+ee;print'
print "baz"$
[download]

That's much less dangerous than I thought at first.

Added again - Quote punctuation can be inserted with dire effects,

perl -e'$with=q/$2$1);print "baz";(/;$_="foobar";s/(foo)(bar)/qq(qq($w
+ith))/ee;print'
baz$
[download]

Uh-oh!