How can one turn regular quotes (i.e. ', ") into LaTeX/TeX quotes (i.e. `', ``'')

Ben said "buttons, dear sir".
I replied "Did you say 'buttons'?" to him.

Ben said ``buttons, dear sir''.
I replied ``Did you say `buttons'?'' to him.

Ben said “buttons, dear sir”.
I replied “Did you say ‘buttons’?”

input:       text+
text:        uquote|squote|dquote
squote       "'" text "'"
dquote       """ text """
uquote:      [contraction|.]+
contraction: [A-Za-z]+ "'" [A-Za-z]+

s/"(w)/``$1/g;
s/'(w)/`$1/g;
s/([w.?!])"/$1''/g;

# A single or double quote before a word character, preceded
    # by start of line, whitespace or punctuation gets converted
    # to "`" or "``" respectively.

    $text =~ s{ ( ^ | [sp{IsPunct}] )( ['"] ) (?= w ) }
              { $2 eq '"' ? "$1``" : "$1`" }mgxe;

    # A double quote preceded by a word or punctuation character
    # and followed by whitespace or end of line gets converted to
    # "''".  (Final single quotes are represented by themselves so
    # we don't need to worry about those.)

    $text =~ s{ (?<= [wp{IsPunct}] ) " (?= s | $ ) }
              { "''" }mgxe

'([ w-]+)'", " `\1'