The first comma was removed from each number.

The s/// operator by default removes only the first match. So:

my $var = "foobarfoobaz";
$var =~ s/foo//;
say $var;   # says "barfoobaz"
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There are various flags you can include to alter its default behaviour though. One of the most useful is the "g" (global) flag...

my $var = "foobarfoobaz";
$var =~ s/foo//g;
say $var;   # says "barbaz"
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Note that the slashes may be replaced with other characters, so you could equally write:

my $var = "foobarfoobaz";
$var =~ s@foo@@g;
say $var;   # says "barbaz"
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Or even:

my $var = "foobarfoobaz";
$var =~ s{foo}{}g;
say $var;   # says "barbaz"
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... which some people might find more readable. Though note that there are a handful of characters (hash, question mark and single quote spring to mind) that trigger special behaviours here (perlop has more details).