In the spirit of TIMTOWTDI, you could also disable metacharacter processing using "\Q..\E": 
my $txt = '1,2';
$txt=~ s/(\d+)\,(\d+)/$1\Q0\E,$2/;

[download]
This converts the "1" to "10".

Unfortunately, simply escaping like "\0" does not work for many cases, because many escape sequences have special meaning .. Eg: \0 starts an octal sequence. See "perldoc perlrebackslash"

             "I'm fairly sure if they took porn off the Internet, there'd only be one website left, and it'd be called 'Bring Back the Porn!'"
        -- Dr. Cox, Scrubs

In reply to Re^3: Stupid question about regex with string followed variable in replacement by NetWallah
in thread Stupid question about regex with string followed variable in replacement by Anonymous Monk

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