Regex: How to reference capture group from variable?

[archetyped]

How do you reference a regex capture group when using a replacement string stored in a variable when using =~ to evaluate a string against a regex? All capture group references are simply returning \1, \2, etc., not the capture group's value.

Simple example:

echo a=testing | mlr put -q '
val = "Test something here";
search = "(something)"i;
replace = "\1";
match = val =~ search;
result = ( match ) ? replace : "";
print "Match result: " . match;
print "Replace via variable: " . result;
print "Replace inline: " . "\1";
'

Output:

Match result: true
Replace via variable: \1
Replace inline: something

The expected output is that both variable-based and inline should be the same. However, the replacement using a variable's value just returns \1, not the actual value from the captured group (i.e. something).

This is a simple example, but in actual practice, I have multiple regex patterns, each with a replacement string that references capture groups in different ways, so a way to turn those capture group references into the captured value would be greatly appreciated.

Thanks!