use strict;
use warnings;

my $renames = {
    this_sub => 'that_sub',
    var_1    => 'var_a',
    var_2    => 'var_b',
    Ignore   => 'FAILED',
    nothing  => 'FAILED',
    and      => 'FILED',
    can      => 'FAILED',
    t        => 'FAILED',
    do       => 'FAILED',
    it       => 'FAILED',
};

my $line = qq/   this_sub("first", var_1, "Ignore ""can't""", var_2) ' do it\n/;
print $line;

my $matched_keys = '\b' . join( '|', keys %$renames ) . '\b';
my $match = qr/($matched_keys)/;
my $vb_string = qr/("[^"]*(?:""[^"]*)*")/;

my @parts = split $vb_string, $line;

my $do_code = 0;
for my $part (@parts) {
    $do_code = !$do_code;
    next unless $do_code;

    if ( $part =~ m/'/ ) {
        my ( $code, $comment ) = split /'/, $part, 2;
        $code =~ s/$match/$renames->{$1}/ge;
        $part = "$code'$comment";
        last;
    }
    else {
        $part =~ s/$match/$renames->{$1}/ge;
    }
}

print join( "", @parts )