You can do that with the quote and quote-like operators, but also, for regexes, with the m// and the s/// operators, which can be written, for example, m{...} and s[...]{...} or even m#...#, etc, as shown in the following Perl one-liners:

$ perl -e 'print $1 if "foobar" =~ m{f(oo)ba}'
oo

$ perl -e 'print $1 if "foobar" =~ m#f(oo)ba#'
oo
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Update: well, thinking again about what I wrote above, m// and s/// are in fact part of the quote and quote-like operators (so Ken's answer said it all), but I just wanted to point out that this can be done in direct regex constructs.