Returns a quoted version of $string that's ok for inclusion in a
"..." string.
The following is a diagram lifted from the B manpage's documentation showing how various ops are related by ISA and what properties each has.
B::OP[next type
| sibling opt
| name static
| ppaddr flags
| desc private
| targ spare ]
|
+--------------+---------+----------+----------+
| | | | |
B::UNOP[first] B::SVOP B::PADOP B::COP B::PVOP
/ \ [sv [padix] [label [pv]
/ \ gv] stash
/ \ stashpv
B::BINOP[last] B::LOGOP[other] file
| cop_seq
| arybase
B::LISTOP[children] line
/ \ warnings
/ \ io ]
B::LOOP[redoop B::PMOP[pmreplroot
nextop pmreplstart
lastop] pmnext
pmregexp
pmflags
pmdynflags
precomp
pmoffset]