Yes, you would check ref($regex->[1]). It will be 'CODE' for a coderef and false (empty) for a non-ref. You could put the whole test/selection into the block like so: 
my $regex = ['(foo)',sub {\"bar$1"}];
my $string = 'blah foo blah';
$string =~ s/$regex->[0]/${(ref($regex->[1]) eq 'CODE' ? $regex->[1]->
+() : \$regex->[1])}/;
print "S=$string\n";

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In reply to Re^3: Regex Substitution, Interpolating on the RHS? by Roy Johnson
in thread Regex Substitution, Interpolating on the RHS? by Cody Pendant

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