Strings are immutable in JS, e.g. a regex replace there requires an assignment to a new variable.

I.e. it's always s///r there.

I'm not sure if I'm still up to date, but the internal text format in JS is UTF 16 while it's kind of UTF 8 in Perl. This requires 2 or 4 bytes /character in JS. So more memory needed but faster to split.°

5 % 2.2 is 1 in Perl but ~0.6 in JS. Perl accepts only the integer part of the arguments. It's documented in perlop but still surprising.

Please note that 50%22 is 6 in both languages.

°) Well IFF the utf8 flag is enabled in Perl that is.