Quoting -replace & variables

Question

This is in response to my previous question:

PowerShell: -replace, regex and ($) dollar sign woes

My question is: why do these 2 lines of code have different output:

'abc' -replace 'a(\w)', '$1' 'abc' -replace 'a(\w)', "$1" 

AND according to the 2 articles below, why doesn't the variable '$1' in single quotes get used as a literal string? Everything in single quotes should be treated as a literal text string, right?

http://www.computerperformance.co.uk/powershell/powershell_quotes.htm
http://blogs.msdn.com/b/powershell/archive/2006/07/15/variable-expansion-in-strings-and-herestrings.aspx

Answer 1

In your second line:

'abc' -replace 'a(\w)', "$1"

Powershell replaces the $1 before it gets to the regex replace operation, as others have stated. You can avoid that replacement by using a backtick, as in:

'abc' -replace 'a(\w)', "`$1"

Thus, if you had a string in a variable $prefix which you wanted to include in the replacement string, you could use it in the double quotes like this:

'abc' -replace 'a(\w)', "$prefix`$1"