Ruby regex- does gsub store what it matches? -

if use

.gsub(/matchthisregex/,"replace_with_this") 

does gsub store matches regex somewhere? i'd use matches in replacement string. example like

"replace_with_" + matchedregexstring + "this" 

in above example matchedregexstring stored match gsub? sorry if confusing, don't know how else word that.

from fine manual:

if replacement string substituted matched text. may contain back-references pattern’s capture groups of form \d, d group number, or \k<n>, n group name. if double-quoted string, both back-references must preceded additional backslash. however, within replacement special match variables, such &$, not refer current match.
[...]
in block form, current match string passed in parameter, , variables such $1, $2, $`, $&, , $' set appropriately. value returned block substituted match on each call.

if don't care capture groups (i.e. things (expr) in regex) can use block form , $&:

>> 'where pancakes house?'.gsub(/is/) { "-#{$&}-" } => "where -is- pancakes house?" 

if have capture groups can use \n in replacement string:

>> 'where pancakes house?'.gsub(/(is)/, '-\1-') => "where -is- pancakes house?" 

or $n in block:

>> 'where pancakes house?'.gsub(/(is)/) { "-#{$1}-" } => "where -is- pancakes house?"