perl regular expressions substitution/replacement using variables with special characters - regex

Question

Okay I've checked previous similar questions and I've been juggling with different variations of quotemeta but something's still not right.
I have a line with a word ID and two words - the first is the wrong word, the second is right.
And I'm using a regex to replace the wrong word with the right one.
$line = "ANN20021015_0104_XML_16_21 A$xAS A$xASA";
#splits = split("\t",$line);
$wrong_word = quotemeta $splits[1];
$right_word = quotemeta $splits[2];
print $right_word."\n";
print $wrong_word."\n";
$line =~ s/$wrong_word\t/$right_word\t/g;
print $line;
What's wrong with what I'm doing?
Edit
The problem is that I'm unable to retain the complete words - they get chopped off at the special characters. This code works perfectly fine for words without special characters.
The output I need for the above example is:
ANN20021015_0104_XML_16_21 A$xASA A$xASA
But what I get is
ANN20021015_0104_XML_16_21 A A
Because of the $ character.

Answer 1

ETA:
Since you get:
ANN20021015_0104_XML_16_21 A A
When you want:
ANN20021015_0104_XML_16_21 A$xASA A$xASA
My suspicions are as follows:
You are not intentionally interpolating the variables $xAS and $xASA, so because they are undefined, they just add the empty string to $line, which is visible in your output. E.g. "A$xAS" is expanded into "A" . undef.
You are not using use warnings, so you do not get information about this error.
Solution:
Use use strict; use warnings;. Always. They save you a lot of time.
When assigning, use single quotes instead to avoid interpolation of variables:
$line = 'ANN20021015_0104_XML_16_21 A$xAS A$xASA';
Old answer:
Since you do not say what goes wrong, it's just guesswork from my end.
I can see a possible accidental interpolation of the variables $xAS and $xASA, which you can solve by either escaping the dollar sign, or by using single quotes on that $line assignment.
You can also build your new string by using join, rather than a regex, e.g.:
$line = join "\t", #splits[0,2,2];

Answer 2

If you had used strict it would have told you that you must declare variables $xAS and $xASA.
If you had used warnings, it would have told you that you were concatenating an uninitialized variable.
Hence the common admonishment: "use strict, use warnings".
You simply need to either put the string in non-interpolated quotes ( '', q{} ) or escape the sigil ($) so that it doesn't try to interpolate what it thinks is a variable.
"" are quotes that will mess with your string
'' are quotes that won't
Lesson: use single quotes unless you want interpolation.

Answer 3

The problem isn't in your substitution; the problem is in the very first line of your code example.
$line = "ANN20021015_0104_XML_16_21 A$xAS A$xASA";
tries to interpolate the variables $xAS and $xASA into $line, and interpolates nothing because those variables are empty. Use single quotes instead of double quotes so that the string doesn't interpolate.
Had you turned on warnings it would have warned you about the fact that you're interpolating an uninitialized variable, and had you turned on strict 'vars' it wouldn't have let you use the undeclared $xAS and $xASA at all.
Finally, you don't have to quotemeta the right side of a substitution; only the left.