BTW, aside from logic issues, I don't know how you came across the idea of using "," a comma as the separator?
Yes, this is "legal and allowed", but the difference between a . and a , can be hard to see.

I would use the default of "/" unless there is a reason not to.
My second choice would be vertical bar.
My 3rd choice would be curly braces - almost never.
I have not ever been tempted to use "," for the separator.

$from_api =~ s,^(\d+)\.(\d{2}).*$,${1}${2},;

$from_api =~ s/^(\d+)\.(\d{2}).*$/$1$2/;
$from_api =~ s|^(\d+)\.(\d{2}).*$|$1$2|;
$from_api =~ s{^(\d+)\.(\d{2}).*$}{$1$2};
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