The string following whatever was matched by the last successful pattern match (not counting any matches hidden within a BLOCK or eval()
enclosed by the current BLOCK). Example:
local $_ = 'abcdefghi';
/def/;
print "$`:$&:$'\n"; # prints abc:def:ghi
See "Performance issues" above for the serious performance implications of using this variable (even once) in your code.
This variable is read-only and dynamically-scoped.
Mnemonic: '
often follows a quoted string.