use warnings;
use strict;

# check with escaped double-quotes inside and outside
# double-quoted sub-strings.

my $string =
  qq{uuu\t\\"vvv\t"notab\t\t"\txxxx\t"\t\tno\\"tab"\tzzz\n};
print qq{$string};

$string =~
  s{ ((?<! \\) " [^\\"]* (?: \\. [^\\"]*)* ") }
   { (my $notabs = $1) =~ tr{\t}{}d;  $notabs }xmsge;

print qq{$string};