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The "/g" modifier specifies global pattern matching--that is,
matching as many times as possible within the string. How it
behaves depends on the context. In list context, it returns a
list of the substrings matched by any capturing parentheses in
the regular expression. If there are no parentheses, it returns
a list of all the matched strings, as if there were parentheses
around the whole pattern.

In scalar context, each execution of "m//g" finds the next
match, returning true if it matches, and false if there is no
further match. The position after the last match can be read or
set using the pos() function; see the pos entry in the perlfunc
manpage. A failed match normally resets the search position to
the beginning of the string, but you can avoid that by adding
the "/c" modifier (e.g. "m//gc"). Modifying the target string
also resets the search position.