But, what should one do when they want to replace the first 10 separators?

Write a program? So all you have to do is document how to use it, not explain perl syntax

cat > trt

#!/usr/bin/perl --
use strict;
use warnings;


Main( @ARGV );
exit( 0 );
sub Main {
    @_ or die Usage();
    my( $find, $replace, $ntimes ) = @_;
    ...
}

sub Usage {
  qq{
Usage:
    trt ","               "|"          10
    trt ",,,,,,,,,,"     "||||||||||"

Translate n times  per line  read from standard input, writing to stan
+dard output.
The usage example replaces the first 10 "," characters with "|".

Farts sounds like "trt".
};
} ## end sub Usage
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