正则表达式：用制表符替换每行的第一个逗号

Question

I am trying to Replace first comma of every line with a tab so that the values will align. I have been trying but below regex I have been testing is not leading me to the correct way.

$data -replace "^[^,]*\,{1}","`t`t`t"
$data -replace ",(.*){1}","`t`t"

Raw: 
First Name Then Last,Exported,Exported,Exported,Exported,Exported,Exported,Exported

Another Long Name,Exported,Exported,Exported,Exported,[______],[______],[______]

Short Name,Exported,Exported,Exported,Exported,Exported,[______],[______],[______]

Name Another Name Last,Exported,Porgress,[______],[______],[______],[______],[______]


Needed Output:
First Name Then Last,       Exported,Exported,Exported,Exported,Exported,Exported,Exported

Another Long Name,          Exported,Exported,Exported,Exported,[______],[______],[______]

Short Name,Exported,        Exported,Exported,Exported,Exported,[______],[______],[______]

Name Another Name Last,     Exported,Porgress,[______],[______],[______],[______],[______]

Answer 1

You can replace the first comma with a tab using

$data -replace '^([^,]*),', "`$1`t"

Here, ^([^,]*), matches start of string, then captures into Group 1 any zero or more chars other than , and then a comma, and replaced with Group 1 backreference ( $1 ) and the tab char.

Alternatively, use a lookbehind:

$data -replace "(?<=^[^,]*),", "`t"

Here, (?<=^[^,]*), matches a , that is immediately preceded with any 0+ non-comma chars from the start of string.

If you want to insert a tab char after the comma that has six more commas after it, you can use

$data = 'First Name Then Last, Exported,Exported,Exported,Exported,Exported,Exported,Exported'
$data -replace ',\s*(?=(?:[^,]*,){6}[^,]*$)', "`$&`t"
# => First Name Then Last,   Exported,Exported,Exported,Exported,Exported,Exported,Exported

Here, ,\s*(?=(?:[^,]*,){6}[^,]*$) matches a , , then zero or more whitespaces that are followed with six occurrences of 0+ non-comma chars followed with a comma and then any zero or more chars other than a comma till the end of string.

Answer 2

If $data is already an array of strings (lines), then I would use -split and join for this:

$data | ForEach-Object { ($_ -split ',', 2) -join "`t" }