Replacing each <TAB> character in a file with a comma character can be accomplished several different ways with Perl. (I guess that's one reason the Perl slogan says There's more than one way to do it.)

My favorite way is like this, from the command-line:

perl -pi.bak -e 's/\t/,/g' myfile.txt

From the Unix (or DOS) command-line, you can invoke Perl just like this to convert the file named myfile.txt. This command edits the file in-place, and makes a backup file named myfile.txt.bak (in case we make an error). The new version of myfile.txt contains the changes you just made -- all the <TAB> characters have been converted to comma's.

The command line options I used here are:

-p

Assumes an input loop around your script.
 

-i EXT

Files processed by the <> construct are to be edited in-place.
 

-e COMMANDS

May be used to enter one line of a script (or, in this case, a one-line script).

I just ran into a situation where I needed to convert a tab-delimited spreadsheet file into a comma-delimited file I could import into a database, and used this exact command.

Note that this is an improvement over the Unix sed command, where you can't edit a file in-place. With sed, you have to open the original file, read it's contents, write the changes to a new file, move the original file to a backup name, and then move the new file to the original file name. This is easier done than said, but requires the use of a shell wrapper. Using Perl to edit the file in-place is certainly much easier.